Possibly the modal jarring experience is that they're talking alone with a nice man who seems pretty normal (if a little awkward), and that guy will just inject a conspicuously racist comment into their conversation. Not like a casual comment that seems unfortunate in context, or an edgy comment in a discussion that was already dancing around race, but something completely out of the blue.

How could such epistemically healthy individuals possibly be racists, literally unthinkable.

I know what actual chuds are like. That being the case, when I see this behavior from rationalists firsthand (again, usually in front of a woman), it often strikes me as bizarre and performative.

Then a few paragraphs later he starts delineating the types of racism he finds acceptable:

people making these comments are usually not "actually" racist. Almost everybody attending a rationalist event is going to be some brand of cosmopolitan internationalist nerd, whether they accept it or not. And if they're not, they're still not going to be racist in the way that a guy from San Antonio whose relatives used the N word at the dinner table is racist. Their "racism" was internalized as a result of a passive and NPC-like relationship with social media, and is fundamentally uninteresting to outside observers.

Basically if you were being racist (charismatically) I don't think OP would have a problem.