I'm confused. Reddit is one of the most anti-racist/sexist communities on the internet. That's the hivemind, so you'd expect anything that's racist or exist to quickly be deleted or pushed to the bottom of the thread where nobody can see it (on the large subreddits anyway).
We most subscribe to very different subs. I've never been a part of a community that had so much tolerance for racism. Some subs have rules against but most do not, and users take advantage of that. On most forums and other communities I've been a part of, you get instabanned for any whif of racism in your posts. On reddit you can pretty much say what you want (in most subs).
I was surprised to find that out, too. Reasonable people unsubscribe from the worst defaults, and don't find out what the unreasonable people who are left there are up to.