You're subbed to the wrong subreddits. You could be getting a lot more out of reddit than you are. The comments here make it sound like 95% of all conversations are about race and politics, but if that's what you're seeing, then that's really just a reflection of what you're reading.
There are subreddits about everything. Most of them don't include conversations about police shootings or Islam.
Yes, the guys wearing white hoods will probably not collectively crap all over the knitting club. That doesn't make the overall situation any better, nor is it a good idea to have them make up a large part of the site's userbase.
(And the only reason it seems that they aren't a problem is because moderators of more specialized reddits have to delete their posts, and ban the posters.)
You seem to concede my point, but then proceed with your argument that it's still a problem, anyway. I don't know how to respond to that except to say that I hope nobody actually listens to you. Reddit has some great communities and people shouldn't be scared to participate in them.
There are subreddits about everything. Most of them don't include conversations about police shootings or Islam.