Unsubscribe from /r/politics. Unsubscribe from /r/worldnews. Find the handful of subreddits that are bothering you and unsubcribe from them. The discussions I read on Reddit are overall nicer than those on HN, not because the userbase as a whole is better, but because it has sewers where the crap is concentrated -- and you can easily avoid them. That's one of their most important features.