They call themselves rationalist, yet they don't have very rational opinions if you ask them about scientific racism [1] [1] https://www.astralcodexten.com/p/how-to-stop-worrying-and-le...
I am not sure precisely it not very rational about that link. Did you have a specific point you were trying to make with it?
If you take a look at the biodiversity survey here https://reflectivealtruism.com/2024/12/27/human-biodiversity...
1/3 of the users at acx actually support flawed scientific theories that would explain iq on a scientific basis. The Lynn study on iq is also quite flawed https://en.m.wikipedia.org/wiki/IQ_and_the_Wealth_of_Nations
If you want to read about human biodiversity, https://en.m.wikipedia.org/wiki/Human_Biodiversity_Institute
As I said, it's not very rational of them to support such theories. And of course as you scratch the surface, it's the old 20th century racist theories, and of course those theories are supported by (mostly white men, if I had to guess) people claiming to be rational