I don't think feminists need to argue directly with people who think rape is a product of evolution (we should go boo them, though, if they make public appearances). In a sexist society, sexist men are bound to come up with silly explanations that help perpetuate sexism. The only effective counterpunch is not a serious counter-argument that dignifies a silly proposition, but the rebuilding of women's movement. The same goes for silly speculations regarding race & IQ, the "cause" of "homosexuality," etc. Naturalization of social categories goes with capitalism & liberalism. So, the point is to demolish the material foundations that give rise to silly ideas.
Yoshie