Do they? Or is it someone with opposing view points that also happen to be racist/belligerent getting banned, and think it's because of their opposing view points rather than being racist/belligerent?
I have no experience with /r/politics but I've seen other subreddits make absolutely no distinction between "having moderately opposing viewpoints" and "being racist/belligerent/troll/brigader", so it results in a ban.