To address the average racial IQ thing, I think that a big part of the left's dislike of it is cognitive dissonance, in a similar fashion to the right's reflexive denial of climate change. They're facts that tend to get used in ways that they find repulsive, and it's easier to deny the fact than it is to make a claim of "It's true, but let's not worry too much about it". In both cases, deniers tend to deny even when questioned in private in my experience(and I'm using friends as my reference group here, so I assume they'd fess up to it being tactical if it was). In both cases, there seems to be a more intellectual strain(which I'm a part of in both cases) that actually does make the "It's real, but who cares?" argument.

(Hopefully that illustrative parallel doesn't turn into an AGW flame war...)