There does seem to be some kind of scientific backing for the stereotype, however. Here's a bit I came across in Rachel Herz's book That's Disgusting: Unraveling the Mysteries of Repulsion:
Closely connected to our repulsion at animality is our disgust at sexuality. ... Sex is among the most brutish behaviors we engage in, and though all cultures have rules for "proper" sex, we cannot escape the fact that sex itself is raw and physical and that we make the beast with two backs quite literally.
Besides being more generally squeamish than men, women tend to be specifically more disgusted by sex than men are. For example, in the first experiment to investigate differences between the sexes in response to sexually explicit films, female college students rated pornographic movies as 20 percent more disgusting and less enjoyable than men did. Many subsequent studies have corroborated the finding that women are more disgusted by sex than men are.
When I read things like this, I always wonder if the disgust the female students are reporting is truly biological or neurological or the result of a lifetime of being told that women don't like sex. I'm also curious about how the specific pornography shown influenced the female college students' response. Are the women more disgusted by sex, per se, or are they more disgusted by something about the way the sex is presented? This seems a significant distinction, though it's all too easy to conflate the two.
For those interested, a nitpicky analysis of the footnotes to the paragraph quoted above:
I want to get hold of the study cited in this paragraph -- D.L. Mosher, "Sex differences, sex experience, sex guilt and explicit sexual films," Journal of Social Issues 29 (1973), 95-112 -- I imagine it may answer some of my questions. But right off the bat, I have to note this study came out in 1973. If female disgust at sexuality is socially based rather than biologically based, then I'd be really interested in an update.
Herz cites another study (in a footnote after the sentence about how many studies have corroborated Mosher's finding), but when I checked out that citation, I wasn't sure how relevant it was. (D.M.T. Fessler and C.D. Navarette, "Third-party attitudes toward sibling incest evidence for Westermarck's hypothesis," Evolution and Human Behavior 25 (2004), 277-94.) It was a paper about how third parties respond to sibling incest, which found women reacted with stronger disgust. Saying women are more disgusted by incest than men are seems pretty different from saying women are more disgusted by sex than men are.
Given my dissatisfaction with these footnotes I wonder if the problem here is that Herz is buying into the cultural stereotype that women don't like sex. If those two citations are the best she's got, I wonder if there really is scientific evidence to back up her statements about women's disgust at sexuality.