Also thinking about whether affirmative action and the desperate impact doctrine are reasonable ideas.

I can't recall anyone on LW advocating those, so you might be attacking a straw man.

That's because they rarely come up. In any case my point is that these doctrines are in place in the USA and the false belief that race is uncorrelated with anything important.

Once you specify where I am, who I am with, what kind of body language the man is using, how big he is, and what he is wearing, further specifying what race he is wouldn't matter that much.

Is that true? Depending on the "where I am" part?

There's only so much you can tell about someone from "what kind of body language the man is using, how big he is, and what he is wearing", after all. In the right racially-segregated society, could it provide valuable additional data?