It comes down to one thing. Does the speech advocate violence or is intentionally designed to cause it against anyone for any reason? If yes,ban it if no, then don't. The other reason is; if someone without proven medical training in a related field is peddling snake oil, ban it. And the twitter taliban thing is actually more complicated than you make it out to be. They are horrible but the government of a country. Its the same reason a certain orange individual was allowed to continue even after calling for violence many times and breaking TOS many times, he wasn't banned until he was voted out of power. Think of it this way, do you want every program to be goven unconstrained access to your hardware without your OS?