I don't think all of that is the result of the "ban wave", it's been a growing trend for years that people prefer echo chambers. That said, if you go to Reddit or Imgur and other sites, you can see the people from Stormfront, /pol/ and the rest are by no means sitting in those chambers without going "abroad".

The issue above all seems to be that not that many years ago, most people who got online did so with a computer, and even though that is trivially easy to anyone here any extra step from "I want online" to "I am online" cuts down the chaff. Now people overwhelmingly stab a button on their phone and bang... the world can hear you.

We're truly approaching a horizon past which everyone is online, and "everyone" includes a lot of marginal characters. The holocaust deniers who used to slip flyers into library books now huddle in their hug boxes, occasionally venturing forth to make some ridiculous claim and flip out at the "sheeple" who don't instantly see their brilliance. Tumblr is... proof that the Right has no monopoly on crazy.

I don't think shutting it down has any benefit, but I don't think that keeping it open does either. It just is.