I rarely understand what his actual position is (outside of contrarianism). In this specific case it's a bigoted thing to say, regardless of whether this is a legitimate threat. Worth banning? I don't know, I don't set rules or own Twitter. A valuable contribution to the open society? Don't think so.

In any case, you use very generalized arguments, hard to discuss them. If you think he is "criticizing" Jewish people (which does not sound like it to me) - do you think it's not an antisemitic thing to do? (To pre-empt your counter-argument... yes, criticizing all white people is also racism/bigotry.) Treating a race, a nation, all followers of a religion, etc as a uniform group that can be subjected to some "criticism" is not an idea that's valuable to the open society. Again, I don't think people should be immediately banned for expressions like that.

If you think we need a "free speech" app filled with these "valuable" ideas - that's fine, just don't expect that it will be a space for discussing opposing views. Places like that always end up on either extreme right or extreme left.