I find it interesting to compare "second tier" 4chan boards like /g/ (technology) to the discussion boards of other websites (like arstechnica). Typically, a place like /g/ compares very well, if not better.
Sites like to blame things like the "Greater Internet Fuckwad Theory", but I think most of the blame lays on the site for having poor moderation.
4chan's moderation is mostly just filtering for child porn. /g/ being good is because it's a niche place. Proper moderation costs proper money, and proper moderation doesn't scale. Moderation can't be the solution.
But crowd-sourced moderation like reddit/HN scales really well: Let the users do the hard work of flagging/voting and a small community of moderators to do orientation-related work.
Outside of /b/ (and one or two 'containment' boards), they do a pretty decent job of modding out hate-speech. Throughout, even on /b/, they keep shitposting (posts intended to do nothing but lower the signal/noise ratio, pushing active discussions towards expiration) way down. I would argue down below the levels seen even on default subreddits. Reddit has a serious shitposting problem.
Sites like to blame things like the "Greater Internet Fuckwad Theory", but I think most of the blame lays on the site for having poor moderation.