I neither upvoted nor downvoted that post, so my guesses at the motivations of downvoters shouldn't be trusted too far, but my guess is that mostly it was downvoted because, while it was ostensibly about a technique of rationality, (1) what it said about that technique was mostly very obvious, (2) a big chunk of the article was devoted to the discussion of an entirely different topic with considerable mindkilling potential, and (3) this gives some ground for suspicion that the rationality-technique discussion served largely as a pretext for airing the author's views on that topic.

See my comment here for why I think the example was appropriate. Furthermore, the way you're throwing around the term "racist ideas" suggests you are also making the mistake the post describes with respect to the example given.

As for the "discussion, particularly here", again that doesn't look to me at all like censorship of right-wing ideas, nor like people arguing for the censorship of right-wing ideas.

You might have missed the part where AndrewHickey says:

If you think that racism was only a problem 'not so long ago' rather than being an ongoing, major problem, then you probably just shouldn't discuss race at all.

Incidentally, I notice that some people in this thread are insisting that there's nothing particularly right-wing about believing in racial intelligence differences, whereas the only thing I can see to link the downvoting of the post you linked to with "right-wing ideas" is its defence of (discussing the possibility of) racial intelligence differences.

Depends on what you mean by "right-wing". It's certainly true that there are currently a number of left-wing people who believe that discussing race and intelligence is morally unacceptable.