I'm not going to split hairs about the actual positions of radical leftists, because it's not really relevant to this conversation.
I will, however, point out, that much of the alt-right is terrified of the antifa boogieman... And that Parler, the platform of free speech was quite happy to ban anything that smelled of antifa... As well as much that could, be described as moderate leftism.
Its tolerance for speech only extends to a very narrow slice of the political spectrum.
Yes, but the notion of an existent, burgeoning "Alt-left" is due to fully attributable for folks being divorced from reality as a consequence of consuming lying media sources (especially those promoted on Parler). Also, "Antifa" isn't an organization. So classifying what white nationalists call "antifa" as boogeymen is surprisingly apt.
What gets blocked on Parler is more appropriately called "not supportive of white nationalism." That way you are sure to capture the entire space of content, whether Alt-right or not, instead of narrowing the universe to Alt-right and things the alt-right is encultured to fear but don't appear in reality.
