Roko Mijic (of Roko's basilisk fame) has written a parable about the suppression race/gender differences, "doing the job Scott Alexander will no longer do" in Kevin's words:
There's a lively debate on mistake vs. conflict in other replies, but we've stretched both concepts (and, accidentally, the principle of charity as well) to the point of absurdity. It's uncharitable to interpret the other party as being delusional (no amount of LW-speak changes this fundamental implication), and it's unreasonable to model conflict theorists as speaking in good faith to those they suspect of using valid information for nefarious purposes. To put it plainly, I think everyone (of note) knows "the forbidden truth" and has various reasons for denying it, some far more principled, rational and self-aware than what mere fashion/virtue signaling implies.
It's natural for a large swath of the population to muddy the waters intentionally. How do I put it... You know, back in 2014 when Russia had annexed Crimea, the first important strike was made by Polite People (as they were memed into Russian public consciousness). It was painfully clear that those are not "self-organized militia" of any kind but simply good old Russian Spetsnaz. But great many people who could easily tell as much began denying it, nitpicking, obfuscating the issue with all rhetorical might they could muster. After Putin admitted that, yea, it kinda had been our guys, there was no shock, no retrieval of previous statements: indeed, many of the deniers just smugly acknowledged that they were bullshitting and sowing doubt to stall for time. This behavior, once noted, led to the concept of "expletive on a secret mission". The idea is that a patriotic Russian civilian feels himself part of a grandiose project of extreme moral importance, and it demands that he helps out on the (dis)information front: covers up for botched operations, signal-boosts helpful if obvious lies, etc. The lies are not convincing him, and he's not lying out of pure evil; they're just way way better for his side than honesty from the start. Perhaps he'll admit to having known truth when it becomes irrelevant to the prospects of the enterprise.
I think this is how most groups act. There's no need to coordinate some "conspiracy" explicitly, when the feeling of discomfort in places where the group's narrative has the greatest friction against reality provides enough of a synchronizing signal. Most college-educated leftists probably would be able to state, if not seeing their project as threatened by outgroup (and themselves by ingroup), their reasons for denying things they know to be true (HBD in this case). Such as: it'll reinforce the loathed social structure dominated by "whites", it'll provoke violence and discrimination, etc. It's not just Dennett and Turkheimer – "foot-soldiers" are also engaging in denialism out of a principled strategy. Occasionally you can read it between the lines. But you can't discuss it openly, because left Straussianism is one hell of a drug; less cynically, people have great trust in the necessity of "the Noble Lie". They see the perpetuation thereof as immensely praiseworthy calling; some actually go into science to acquire credentials which make it easier. How they became so convinced, I'm not sure.
Good luck convincing them that you're one of the good guys, Roko.