Reddit, itself, is, or at least used to be, a variety of diverse communities. I don't care about either /r/FatPeopleHate or /r/FatPeopleLove I don't consider myself a part of those communities. I subscribe to subreddits I want to track, and I am not a member of the ones that I don't.
Surely people on the disagreeable side of the psychological spectrum will gravitate towards some communities and people on the opposite side of that spectrum will gravitate towards other communities. Some communities are cross-cutting, and so have to be moderated in a different way altogether (which Reddit already accommodates). Other than that, communities have their own social protocols. Creating blanket rules / bans / restrictions across communities restricts the organic nature of human interaction and hamstrings it in a rather depressing way.
Many problems arise in the battle for "front page" or "trending" screens that try to blend content from multiple communities and invite competition or "raids" or what have you from opposing sides. Personally I hate such things, I have no desire to be manipulated by them and use browser extensions to block them. But given that they exist, it's again mainly a moderation / preferences problem. Give the control to the user over what they want to see.