[anticonformist]

The ethics are the issue. If protesters were unable to stop the extremists, that would be one thing. They're unwilling and uninterested in stopping them, and that is the ethical issue.

This is exactly the same reason police officers are ethically in the wrong. They could decide that "enough is enough" and push out the "bad apples" among them. Instead, they do nothing. That is their ethical failing.

The protesters (and their supporters) are doing the exact same thing, ethically. They refuse to even attempt to push out the extremists, as evidenced by the widespread rationalization and minimization of their actions.

These are very basic ethical dilemmas. Do you or don't you call out and punish bad actors among your group?

Ancient tribes were generally okay with anyone of their tribe committing any atrocity as long as it was against a member of a foreign tribe.

Civilized people condemn and punish even members of their own tribe and do it even when the victim is a member of a foreign tribe.