Here is an excellent post by David Friedman on the anti-scientific race and gender difference denials:
The denial of male/female differences is the most striking example of left wing hostility to the implications of Darwinian evolution, but not the only one. The reasons to expect differences among racial groups as conventionally defined are weaker, since males of all races play the same role in reproduction, as do females of all races. But we know that members of such groups differ in the distribution of observable physical characteristics--that, after all, is the main way we recognize them. That is pretty strong evidence that their ancestors adapted to at least somewhat different environments.
There is no a priori reason to suppose that the optimal physical characteristics were different in those different environments but the optimal mental characteristics were the same. And yet, when differing outcomes by racial groups are observed, it is assumed without discussion that they must be entirely due to differential treatment by race. That might turn out to be true, but there is no good reason to expect it. Here again, anyone who argues the opposite is likely to find himself the target of ferocious attacks, mainly from people on the left.
Next consider the whole nature/nurture debate, in which the left has, for half a century or more, mostly taken a strong pro-nurture position. It is hard to see how humans could have evolved intelligence if intelligence is not heritable.
This parallels Jonathan Haidt’s description of liberals in social science. Something like, ‘Prenatal exposure to hormones are all well and good for gender differences in animals, but the idea that it could be in humans. How sexist!’
