I already know I sinned by trying to have a productive conversation of twitter, however when "talking" with a few self proclaimed communists (no, I don't think they were joking) they basically implied the "rich" deserve to die, they were morally allowed to kill them, etc. IIRC, this was on a post about a teachers union displaying a guillotine and I pretty much said "yea, lets not be like this." There was also some racism thrown in there, I guess for good measure. They seem to have even developed their own "secret language", calling white people 'mayos' and 'yts' - maybe to get around filters? Or just to be extra edgy.
I would argue that pushing some justification of murdering fellow citizens because of their net worth is just as dangerous as the insane conspiracies about lizard people... if not more. Yet, I don't think these things are shut down or given the same standards as what you're thinking of.
I wish for twitter (and everyone else's sake) they equally applied their "TOS". I have no need to go to those sites you mentioned... in fact I can't think of anything less productive but on the flip side of the coin, I've pretty much deleted twitter for the same reason.