An interesting thought experiment is to look at all the "for-fun" online communities that you've been a part of. For instance, game forums, enthusiast subreddits, etc., and see how the discussion there varies from discussion on political things. Of course it will be different, but I think I have started to see factionization in the larger online communities that I am a part of. However, it's hard to know whether this is human nature, or something learned from other sources. (For example, a user who visits political subreddits and then takes that attitude to the Hearthstone subreddit.)