The main terrorist threat in the US comes from US citizens with right-wing views.

This threat is exacerbated by the right-wing bias of thugs in general. "The FBI is … a political police force that primarily targets the left."

After right-wing extremists stabbed antifascist protesters including supporters of BAMN, the FBI investigated the antifascists as a possible threat to the rights of the right-wing extremists (which the FBI identified as "KKK").

I can understand, given the right-wing bias of federal and state thugs, why antifascists would be tempted to reject the idea of respecting freedom of speech for right-wing extremists.

But that is a fundamental wrong. Freedom of speech covers all views, and we must not advocate denying it to views we abhor. Antifascists had better support freedom of speech for all views, or (as these events demonstrate) the antifascists will be the ones persecuted.