Many analytic philosophers have written about sex and gender. An early collection that might be a good place to start is "A Mind of One's Own: Feminist Essays on Reason and Objectivity" edited by Louise Antony and Charlotte Witt (1993). A more recent collection, a product of the Society for Analytical Feminism, is "Out from the Shadows: Analytical Feminist Contributions to Traditional Philosophy" edited by Sharon Crasnow and Anita Superson (2012). The website of the Society for Analytical Feminism is at https://sites.google.com/site/analyticalfeminism/home and has many useful resources.
We are all fallible. Even experts. Especially about matters as value-laden as questions of "normality" of types of human beings. If you disagree with Amaury de Riencourt, and give reasons for your disagreement, then the fact that you have no credentials would not matter. Your reasons should be evaluated on their own terms.
This particular claim about gender and normality is difficult to agree or disagree with because it is so vague. You think the statement implies that to be male is to be "abnormal"; but it may only mean that to be male is to be a variant (non-standard form). (I don't know the work of Amaury de Riencourt, so I do not know what is meant, and whether it is a biological, sociological, political etc claim.)
The questions that you are asking are terrific! They can also be taken further. E.g. is it necessary for you to assume that there are strictly two biological sexes? (I don't think so). Or e.g. What is wrong (if anything) with sexualization of a group? What is wrong with sexualization of a subordinate group? It is not difficult to turn up inconsistencies in what society considers to be socially normative.
You ask a complicated question very simply! Here's some advice about how to pursue this topic, with a few oversimplifications of my own. Sex (physical sex) is often distinguished from gender (gender identification in people, often culturally influenced) as well as from sexuality (sexual orientation). Intersex people have bodies that are not "typically male bodies" or "typically female bodies" but have elements of both. This ranges from (controversially) hypospadias in men (the urethra not opening at the tip of the penis) to individuals with both an ovary and a testis. Anne Fausto-Sterling's excellent book Sexing the Body describes the range. Then the question is, do we regard intersex individuals as "abnormalities," and thereby preserve our traditional understanding of biological sex as a binary, or do we regard intersex individuals as counterexamples to our traditional understanding of biological sex? Some (including Fausto-Sterling) appear to think that the answer to this depends at least in part on the prevalence of intersex persons. I prefer the approach of Joan Roughgarden Evolution's Rainbow, who explores the biological significance of sex and its variability across the plant and animal kingdom. I think she shows that are biological reasons (from evolutionary considerations etc) for giving up the binary conception of gender.
(Intersex should be distinguished from "transsex" in which individuals have sex typical bodies but different gender identity. Both should be distinguished from sexual orientation.)
Most constructivists think that assigned sex has something do with physical bodies; but how physical/biological information is incorporated into gender categories can vary depending on cultural, historical, pragmatic etc interests.
Genitalia are one way in which we assign gender, but not the only way; we recognize, for example, that genetic males can have external genitalia indistinguishable from those of "normal" women (Androgen Insensitivity Syndrome), and that genetic females can have masculinized genitalia (Congenital Adrenal Hyperplasia). There are also true hermaphrodites (individuals with both ovarian and testicular tissue). And then there are transsexuals who look one way and yet are "gendered" another way. There have been some cases of parents/doctors choosing the gender of an ambiguous infant, and sometimes the gender identification takes, sometimes it does not (we do not all have an inborn gender identification that resists change, although many of us do, and for most of us it coincides with physical sexual characteristics).
Some interesting reading on these topics--Alice Dreger's work on intersex (you can find it at www.alicedreger.com) , Anne Fausto-Sterling's Sexing the Body and Joan Roughgarden Evolution's Rainbow.
Iris Young's "Throwing Like a Girl" is a wonderful description of gendered experience. Our experiences of the world are influenced by many factors that have to do with our positions in the world, both our physical positions (biological sex, physical disabilities) and our political positions (race, gender, social class, power). "Experience" is defined broadly to encompass all we are conscious of (some call it phenomenological experience). I recommend Kay Toombs work on the phenomenology of disability as another rich description of perspective.