is there any evidence to support the idea that having places for hate speech to grow has a quarantine effect, reducing hate speech elsewhere? Studies on the effects of banning hate speech communities suggest that the mechanics don't work that way. For example, when reddit banned /r/fatpeoplehate and other subreddits centered around hate groups, other subreddits did not inherit the hate speech problem, and former hate group users reduced the amount of hateful content they posted.

http://comp.social.gatech.edu/papers/cscw18-chand-hate.pdf

If you spread them among fragmented communities, the "clean" communities remain the louder voice on the internet.

Is that a good thing? Seems when extremists get together with only other extremists, they become even more extreme.

Wasn't 8chan a containment board as well?

There are plenty of other alt-right hangouts, and probably 3 more already started today.

They still have their own echo chambers. thedonald[.]win, Gab, and Parler come to mind.