Short answer, no, Carleas is not “a white supremacist a nazi [sic]”.
This is accurate and unfortunate. It’s a race to the bottom, where any platform that tolerates bad ideas becomes a black hole of bad ideas.
There is also no room for compromise. I can’t imagine that many people would be satisfied by there being “only one” antisemitism thread, so that it was contained and didn’t erode every other discussion. Because in that case, people who want to post serious philosophy, who want to write something worth sharing, will have their quality philosophy next to elementary school racist garbage. That’s going to bring the discussion down.
But the solution is to ban certain ideas, i.e. to say, you can’t post ideas that are racist, sexist, bigoted in any number of ways. Most of the internet has gone in this direction, because most sites are for-profit, and as BarbarianHorde’s link notes, private companies support free speech only insofar as it supports their bottom line. Even Cloudflare, which actually took a principled stand about the content of the sites in its network, ended up caving when enough people threatened to boycott.
That’s a problem. Free speech doesn’t need to be curtailed by government, because the heckler’s veto has become so effective in the private sector. Maybe that’s a good thing when it comes to Nazis, but it never stops at Nazis: once we accept the argument that some ideas are so bad that they must be silenced completely, people will appeal to that argument for whatever ideas they don’t like. That’s antithetical to progress, to understanding, to philosophy.
I will police people who are dicks and undermine discussions by injecting their pet hate where it isn’t relevant, or for harassing people for their perceived identity, or for presenting ideas for shock value rather than to defend the idea dispassionately. But I will not ban ideas, no matter how wrong, how ugly, how distasteful.
The solution to bad speech is more speech. Argue with bad ideas, because they don’t hold up to scrutiny.