You're in luck. We have an entire topic devoted to philosophical questions pertaining to sex. You can browse through it here:
Someone might say that punishment should fit the crime and therefore that raping rapists is a just punishment. Someone might also say that torturing torturers is a just punishment. My reaction is that examples like this show the unacceptability of a strict "eye for an eye" notion of justice. Torturing someone as a form of punishment strikes me as depraved; so does raping a rapist. Torture and rape are crimes that show an utter and complete lack of respect for the victim's humanity. That's something that an acceptable judicial system should avoid, in my opinion.
As for your hypothetical about rape in the case of near-extinction, I don't feel the force. Why is the continued existence of humanity so important that it would justify raping an unwilling woman and forcing her to carry a baby? Is the sort of "civilization" that would stoop to such things work preserving? What's so hot about humanity from the point of view of the cosmos?
Are there any circumstances that would justify a different conclusion? Perhaps there are hypotheticals so horrifying that the answer is yes. But that's the point: those hypotheticals would indeed be utterly horrifying. They're unlikely (one hopes!) to give us any guidance in the kinds of situations we're likely to face.
In answer to your first question ("Is kissing a person on the lips other than one's spouse cheating?"), the very idea of "cheating" (conceptually) involves breaking a rule or agreement or promise, and so kissing someone other than one's spouse on the lips would be cheating if you had an agreement (explicit or implicit) that one would only kiss one's spouse on the lips, just as you would be cheating if you cried or laughed or sung a particular song with another person if you had promised only to do so with one's partner / spouse.
Before moving to your suggestion about promises, a brief note: I am a little curious about the example you give of kissing as there are many cultures (I have no idea how many) when kissing another person (who is not one's spouse) on the lips is not at all unusual or thought to be even remotely sexual (and thus a domain in which sexual fidelity would not be an issue). Actually, in the first two centuries of Christianity in Europe, unmarried men and women would regularly kiss on the lips during religious services in what was called "the exchange of the peace" though apparently this practice eventually needed some regulation for by the third century you can find precepts that the kissing should not involve open mouths and nor should the kissing be repeated multiple times during the same service! Thinking about this a bit more....I believe that (in general) it is quite common in many cultures for adults to kiss their children and other relatives and good friends on the lips without there being any implications about sexuality and thus not a matter of sexual fidelity.
Over to your suggestion about vows..... Your example of a vow or promise is: "I love you so long as you fulfill and do such and such...conditions according to MY needs of such and such..." As I acknowledged at the outset, these are private matters and there is no official philosophical policing of vows.... Still, I suggest three things are worth considering (and these might be more of a reflection of my personal dispositions rather than reflecting "objective values"): first, in entering a committed relationship though the testimony of "I love you" I suggest there is a kind of self-offeirng. Your are giving yourself, and your needs... over to the other, and he / she is giving him or herself over to you. So the promise is not, first and foremost, about "MY" needs as "OUR LIFE" together. Second, while it seems natural and expected that a marriage or relationship commitment would be conditioned on "the other" (it would hard for me to stay married to my spouse if she chose to divorce me and marry a lesbian), but loving each other is another matter. I hope my promise to love my spouse is unconditional even if she ceases to be my spouse and expressing my love for her becomes something entirely different than it is now. Third, over to promises and kissing...... If we set aside the many conditions in which kissing a non-spouse on the lips is permissible and expected in many circumstances .... let's let the focus be on the following:in a relationship in which one has promised to be faithful sexually with one partner, but the promise has been a bit vague (for example, there is no fine print on whether it is unfaithful to hold hands with a person who might be a potential love-interest outside the primary relationship). Under those conditions, I suggest a faithful partner would err on the side of being extra careful that one's actions with others do not send the message of (or actually express) desiring "to cheat." Intimate trust is such an achievement that can take years to develop... why risk it by doing acts that might well be interpreted by one's partner as sending the message that one more committed to having one's own needs met even if this means severing a committed relationship rather than seeking to have your and her needs met in the relationship you both entered through the door of promising to love one another?
You have raised a question that goes to the heart of one of the most serious relationships: what is the moral role of fidelity and respect in terms of sexual relationships? For many of us in 'the west' the 'cheating' would be equally wrong for a male or female. Just as it would be equally wrong for a male or female to cheat in other areas of life to steal money from innocent children it would seem to be equally wrong for either to cheat on each other. But there are different social, cultural expectations that come into play in some places today that reflect an old, patriarchal bias that tends to look more strictly at cases of adultery or infidelity involving females rather than males. I suggest that there is no viable ethical or religious or evolutionary ground for this imbalance or unfairness today. So, while I suspect that any justification that gives greater allowance to the male is a reflection of distorted values, a perversion of a mature religion or simply bad anthropology, it should probably be conceded that there are some social contexts today in which male fidelity is regarded as especially noble, a reflection of good judgment involving greater, intentional resolve, than female fidelity, owing to the greater expectations and opportunities in some social contexts for males to violate their promises of fidelity. From my point of view, this is regrettable. TO BE CLEAR, I do not think it is regrettable that women do not have equal expectations and opportunities for infidelity as males have in such contexts! An ideal society, in my view, would not be one in which all couples of whatever gender are encouraged to form lasting commitments to fidelity and then encouraged to have optimal opportunities to betray each other in ever more tempting, exciting conditions! But...... allow me one more paragraph about the special bond of sexual fidelity and why one should treat male and female fidelity and infidelity in the same way, irregardless of whether one's society is sexist.
Consider two kinds of relationships: one in which persons are boyfriend and girlfriend, and the other involving marriage.... I imagine that in the first case there is sometimes an assumption of fidelity or monogamy but not a solemn vow and maybe at most a general agreement about honesty. I suggest that the dishonesty involved with cheating at that stage in life would be on the same level of seriously lying to one another --a likely element, presumably, in most cases of "cheating" otherwise why would we call it "cheating"? But once there is a solemn vow as in marriage or the equivalent it seems that there is a more grave wrong, requiring confession, repair, forgiveness, reconciliation, if the relationship is to survive and perhaps even in the best case even become stronger and deeper for both parties loving each other enough for there to be reconciliation. When one takes seriously the potential beauty or ugliness of how this intimate relationship, protected and bound by vows, is lived out, I suggest that the two parties are first and foremost equally answerable to each other and not to the social institutions and patters of life around them. So, in most cases of marriage, the vow of fidelity is made between the persons. For those of us in different religious traditions, the vows may be made "in the presence of God" or the families or communities, but these in many if not most are cases in which the vows are WITNESSED. For Christians, for example, there may be a prayer that God would bless the marriage and grant strength and grace for their flourishing, but the vows are made between the persons who marry. Thus, if I betray my husband, I am not betraying a vow to God or my family or community. I am betraying him. In this sense, I suggest that even in a sexist society that might grant more "freedom" to one gender or the other, "society" is not the thing that persons make vows to when joining together to form an intentional relationship. It is, I suggest, within that intentional relationship of the two persons who have made promises to one another that the morality or immorality of each other's actions, motives, desires, and intentions will be forged.
Because, for every X, there is a philosophy of X, it should come as no surprise that a well-known philosopher has written a book on this subject! I refer you to Richard Taylor's Having Love Affairs (Buffalo: Prometheus Books, 1982), isbn 0-87975-186-X, http://www.amazon.com/Having-Love-Affairs-Richard-Taylor/dp/087975186X
Probably one of the main reasons we shy away from talking with others about sexual attraction unless we are doing so with a partner in a sexually intimate relationship or conversing with a therapist or discussing medical issues (from STDs to pregnancy to birth control) or advising a friend who has asked for advise, is because we see sexual matters as amazingly / profoundly personal and we would find it positively intolerable being told by all sorts of people whether they find you sexy or not. Imagine that in the course of sitting in a coffee shop for an hour you are set upon by hundreds of people who tell you all about their sexual desires as grandmothers who like to have sex while cooking apple pie, former medical students who were expelled from medical school for public nudity, lawyers who have been accused of sexually harassing interns, politicians who will say anything or do anything to get your vote, two tax collectors who have strange, contagious rashes all over their hands and faces and want to touch you.
Back your observation about an elephant in a room: someone's interest or lack of interest in sex with whomever and whenever is rarely (in my experience) a matter that is as easily spotted as an elephant, even a small elephant. But if you do find joy and satisfaction in an intimate relationship, there will be a time and place when "pillow talk" will be so valued, in part, because it is private and such intimate things cannot remain intimate while being talked about as though one is talking about seeing elephants at the zoo.
What counts as a cause is certainly a philosophical question, and although both laypeople and scientists often confidently talk about causes, philosophers are far from unanimous about the correct analysis of the concept of causation. It's a matter of considerable controversy: see, for example, this SEP entry.
But if we achieved a precise enough and plausible enough understanding of cause and a precise enough and plausible enough understanding of the concept homosexual (perhaps easier but by no means easy), then I think the question of what causes homosexuality would be purely empirical rather than philosophical. It may not be a purely biological question (again, assuming we understand biological precisely enough), but I don't think it would be, at that stage, a philosophical question. Still, lots of philosophical work would need to be done before the question became well-enough understood to be answerable empirically. Or so it seems to me.
I don't know how much older you are than the women you watch with, and I don't know anything about the larger situation. I don't know why you aren't picking companions closer to your own age, and I don't know anything about the young women and your relationship with them. What I'd think in detail would depend on all that. But generalizations about "society" are typically pretty vapid. Does "society" mean "most people?" How do you know? Do you have any real evidence as opposed to impressions, anecdotes and a look at website comments by high-schoolers? And most important, what does this have to do with whether you should be doing what you're doing?
We can agree that the high-schoolers should have kept their comments to themselves. We can also agree, at least for argument's sake, that a 19-year-old could make a clear-eyed, responsible decision to make a porn. But that's not the issue. The issue is how you should be dealing with the particular young women you're talking about, in the particular circumstances you all find yourselves in.
You've given a couple of good reasons for being uncomfortable. They'd still be good reasons even if there are a lot of judgmental hypocrites around. There probably are other reasons as well. Do the reasons add up to the conclusion that you shouldn't be doing what you're doing? I'm not about to say. What I'm willing to say is that it would be a lot better to explore your moral discomfort directly without turning to vague, irrelevant generalizations about "society." That kind of deflection is a recipe for rationalization rather than honest self-assessment.
And one more thing: you're absolutely right to be wondering about the point of view of the women you watch with. You might consider actually talking with them about it, in a setting where everyone concerned will feel free to be honest.
There is generally a big difference. Soft core can involve nudity, fashion does not. After all, the point of the latter is to sell clothes and although models may not wear many clothes, they will wear something.
It is a mistake to think that images which are capable of being sexually provocative are all the same.
It seems to me that you are running together two very different claims about the effects of alcohol on persons' abilities to make decisions: (1) that alcohol can lead you to make choices that you would not have otherwise made (and so to consent to things you otherwise wouldn't have consented to); and (2) that alcohol can impair your ability to make genuine choices altogether (and so can make it that you are incapable of consent). The question of rape concerns whether or not the other person has consented to sex, not whether or not the other person will regret later consenting to sex. And so, a man is not "responsible for knowing when his sexual actions will lead to a regretful state of mind in a woman." He, like everyone else, is responsible for knowing that the recipient of his sexual advances has consented to them.
I'm not sure that the "dangerously entrenched orthodoxy" you mention is actually as entrenched as you think. The view implicit here seems to me to be just as popular in our culture and so seems just as good a candidate for an orthodox position, and one that strikes me as dangerous. For the view seems to be one that adopts a stance of skepticism about any accusation of rape against a man, one that thinks it likely that the woman did consent and is only now claiming it was rape because she now regrets consenting to sex. I see no reason for thinking that the real problem is not that many women, at some point in their lives, will be victims of sexual assault and rape but rather that many men, at some point in their lives, will be falsely accused of rape by women who regret having consensual sex with them.
Also, it doesn't seem to me that men, in particular, are "taught that they are in control of their impulses." Rather, much of the culture seems to think that men are not quite in control of their sexual impulses, that men can be provoked into raping by the way a woman is dressed, etc. (since what else could it mean to point out, about a rape victim, that she was "dressed provocatively"). Indeed, the observation that "boys will be boys", when used to excuse sexual harassment, sexual assault and even rape, seems quite clearly to claim that men are not entirely in control of their sexual impulses and so we ought not hold them to a consent requirement that assumes such control.