I take it you don't browse many comment threads, then. Anything vaguely related to black people or Islam and they are virtually guaranteed to show up, spreading their soundbites and gotcha's.
Of course I read the comments. Two comments, here:
1) We don't have a lot of conversations about race or Islam or intersectional feminism (or whatever) over on the credit card churning sub (for example). Not everything is political.
2) Of course, we do have a lot of these conversations on /r/stlouis, some of which, I'm sure, include comments the Hacker News contingent would find obnoxious. But, you know what? They're fine. We get through it. It doesn't dominate every thread. People are downvoted when they're particularly vitriolic. And it's mostly names I recognize from other threads (not outsiders brigading). It's really not a big deal, like, at all.