Why is it so difficult for a forum to accommodate different political views? Is this a problem of human nature? The idea of a uncensored reddit it a good one,

Why is it so difficult for a forum to accommodate different political views? Is this a problem of human nature? The idea of a uncensored reddit it a good one, but the first thing I see going to the page is an administrator complaining that they apparently cannot effectively ban "nazis". https://raddit.me/f/lobby/6159/we-re-being-brigaded-by-nazis-with-too-much-time-on-their https://raddit.me/f/lobby/6159/we-re-being-brigaded-by-nazis... From the comments I've read here, it definitely seems as though the site has the typical heavy handed administration banning opinions it disagrees with. Why can't any of these sites just allow people of all political ideologies to post? 4Chan is the only site I can think of which has never had censorship of this sort. Why is this such a difficult thing to accomplish?