Is there anything that you consider proven beyond any possibility of doubt by both empirical evidence and pure logic, and yet saying it triggers automatic stream of rationalizations in other people?

• Hitler had a number of top-level skills, and we could learn (some) positive lessons from his example(s).

• Eugenics would improve the human race (genepool).

• Human "racial" groups may have differing average attributes (like IQ), and these may contribute to the explanation of historical outcomes of those groups.

(Perhaps these aren't exactly topics that Less Wrong readers (in particular) would run away from. I was attempting to answer the question by riffing off Paul Graham's idea of taboos. What is it "not appropriate" to talk about in ordinary society? Politeness might trigger the rationalization response...)

Wrongbot, I wanted to note a disparity between what you say here:

The most recent common ancestor [chimpanzees] share with humans lived somewhere between 3 million and 800,000 years ago.

and what that Wikipedia article on bonobos says twice:

The chimpanzee line split from the last common ancestor shared with humans approximately six to seven million years ago.