When a human child is brought into existence, whose moral responsibility is it to see that this child’s very significant needs are met? In most human societies, this responsibility has been given to its parents. It was due to the parents’ actions that this child came into existence in the first place; and, further, parents tend to have stronger instincts than others to meet the very significant needs of their progeny. For these reasons, the allocation of primary responsibility to meet the needs of immature humans to their parents generally makes good moral sense. To what extent and under what conditions this responsibility should also be shared with others and to what extent and under what circumstances this responsibility may be relinquished to others are further complicated moral questions.
You wonder whether it is fair that fathers who have had no say in whether a fetus is brought to term should be held morally responsible for meeting the needs of their progeny. This, it seems to me, is a legitimate moral question. But I wonder whether we are looking at the situation in the right way. It seems to me that so long as fathers do not take on an equal share of the responsibility for meeting the needs of their progeny, the decision whether to abort a fetus (if such a decision is to be made available to anyone) must be given to women. For, as a matter of fact, and whether fair or not, most women bear the primary responsibility for meeting the needs of their children. It seems to me that if men wish to be granted the right to play an equal role in deciding whether a fetus for which they are responsible is brought to term, they must also be willing to play an equal role in meeting the needs of their children.
For what it's worth, I find it obscure why someone would wish to pursue this course of action, but I don't find it obviously to be morally objectionable in any way I don't find abortion morally objectionable.
Suppose the woman instead removed the fetus without its being killed, and put it in some kind of suspended animation. Perhaps she thinks, "Well, maybe later I'll be ready for a child, and then I'll continue the pregnancy." It's not obvious why this would be any more objectionable than abortion, and I certainly don't see a difference between this case and the one in the question. Indeed, one might wonder whether, at certain very early stages of pregnancy, there is very much of a difference between this and what routinely happens in fertility labs.
I sometimes call this the "Ronald Reagan argument"; President Reagan was fond of a version of it that, as I recall, had to do with a man in a ditch who might or might not be dead. That also raises a preliminary issue. The question presumably isn't whether the fetus is biologically alive; it surely is. The question (or part of it anyway) is what this living being is. One common way of putting it is to ask whether the fetus is a person -- a being with the same moral standing as you or me. And so I'll put what follows in those terms.
The first thing that strikes me is that there's a glitch in the analogy. In the execution case, the being we execute is unquestionably a person who is possibly innocent. In the abortion case, the being is possibly a person, though if a person, then an innocent one.
This hardly settles the matter, of course. The reply might be that in either case, we run the risk of taking the life of an innocent person; the position of the word "possible" simply locates the source of the risk. But that's too simple. In the typical execution case, what we worry about getting wrong is a matter of fact; the person either committed the crime or s/he didn't and the concern is that we may be mistaken about that. The abortion case is different. Whether or not a fetus is a person seems to be what someone once called an essentially contested question: there may be no straightforward fact to be had. Fetuses are like paradigm cases of persons in some ways, and unlike them in others. A glance at the history of the debate makes it clear that two people can agree about all the background facts (genetic make-up, brain development, etc.) and still disagree about whether the fetus is a person. It's harder to cook up a case like that when the question is whether someone committed murder.
There's another difference: the thought of executing an innocent person makes our blood run cold when we think about it from the victim's point of view. Imagine yourself knowing full well that you've been convicted of a murder that you didn't commit, and that you're about to have your life taken away from you on the basis of a mistake. It's a horrifying prospect. Abortion holds no such horror from the fetus's point of view, because the fetus doesn't have a point of view. It has no conception of its future, let alone of itself.
Just to be clear, my point isn't to settle the abortion issue. After all, newborns don't have anything like the developed point of view of a paradigm person, but infanticide still strikes us as wrong. The point is simply that the Ronald Reagan argument, in its various versions, is too quick.
It's perhaps worth adding that a child has a lot of different rights, and these to different degrees, and there's no particular reason to suppose that these have to come all at once. As a blastocyst becomes an embryo becomes a fetus becomes a child, it would seem that it might acquire these rights, to varying degrees, as it develops.
I think you are right on the implications of allowing abortion morally. It does suggest that there could be a quality of life so low that life would not be worth either initiating, or continuing. And that does not seem a ridiculous idea, does it? We say this of animals, and end their lives when it seems to us not worth their while continuing it (although cynically it might sometimes be a matter of its not being worth our while, I suppose). Why should it not also be the case for human beings?
One way to approach this question is to think about what sorts of properties are morally significant. Some properties--such as the capacity to suffer or feel pain--might belong to a developing human life at some stages, but not others. A zygote probably doesn't feel pain, but it's plausible that an eight month old fetus does.
There are obviously profound moral issues in the abortion debate, and I for one, while respectfully disagreeing with the Catholic Church's position on the legality of abortion, can't even begin to understand its opposition to birth control. And perhaps it is worth emphasizing, for the record, that it is with this aspect of the Church's position that I disagree. Like most who would defend its legality, I am not a fan of abortion.
That said, however, it is unfair to accuse opponents of abortion of the sort of hypocrisy you do. While they may or may not be right in their desire to see abortion criminalized, many of those who hold this view do actively assist pregnant women in placing their children for adoption. The Catholic Church, for example, has long actively supported adoption. That is not to say there have not been controversies in this area, too: Some adoption agencies, especially in Latin America, have been accused of discouraging women from placing their children for adoption. But that is a somewhat different matter.
I agree with Richard that Thomson's analogy doesn't apply to the AIDS victims, as opposed to the virus. I wanted to add something about the reliability of thought experiments in general, though. Philosophers like Thomson (and Kamm) employ imaginary examples in a quasi scientific manner. The example, or rather a consideration of the example, is like an experiment. Our intuitive reactions to the examples are the results of the experiment--the data. We are then supposed to construct moral theories that fit the data. The problem is that our moral intuitions are influenced by all kinds of factors, including ones that those same moral intuitions tell us are morally irrelevant. A pretty good examination of this problem is contained in Peter Unger's excellent (but slightly annoyingly written) book Living High and Letting Die. This doesn't mean that we should abandon imaginary examples altogether. They can serve as a pretty good consistency check on a position, for example. But we certainly shouldn't have a lot of confidence that our intuitive responses to imaginary, and often highly unrealistic, cases are reliable indicators of moral truth.
Yes, I understand what you mean. I've also been known to smile wryly when reading "Abortion Stops a Beating Heart" (as does taking someone off a respirator, killing a mouse or even a spider). Perhaps more controversially, "Women are Not Incubators" (many are, though none are "mere" incubators) and "Keep your Laws Off My Body" (the same body that even traffic laws, rape laws, smoking laws and indecent exposure laws constrain). Then there's "Abortion was a Nazi Program" (as was the Autobahn highway and the Volkswagen). But I must admit that after indulging myself in a sense of logico-philosophical supercilousness for a moment, I suppress my feelings of superiority and think perhaps that you and the other critics here should reconsider. Remember that what you're reading is a bumpersticker and not a philosophical or legal treatise. I agree that political discourse seems a rather paltry thing today. But that doesn't change the fact that we're dealing with a rhetorical form here to which the kinds of criteria you bring to bear only loosely apply. For myself, I'm glad to see people express their political views in this format. Like the other critics, however, I do wish its limits weren't characteristic of so much of the rest of the political discourse today.