It's tempting to want to blame the admins or political bias...the main problem are the mods for individual subs. Too much domain and keyword filtering, arbitrary removals of content, algorithmic removals/filtering, etc. The whole point of moderating is to actually moderate, not remove stuff automatically all the time. Even content that gets up-voted and users like, will not uncommonly be removed for no reason. If they don't want to moderate, they should be removed by the admins and replaced by new moderators who will. The tendency as time goes on is for subs to become increasingly moderated and censored to the point of being useless.