It's also a clever little bit of legal CYA. Coordinated inauthentic behavior' = fake accounts amplifying things. Actual extremists posting on main and organizing on FB? A-OK as long as they exercise a bare minimum of discretion and avoid discussing specific illegal activities.
I'm not sure I follow your logic. "fake" seems like a completely wrong word to use to describe actual extremists (but I completely agree they should do more to police extremist content).
Coordinated inauthentic behavior describes exactly what it says on the tin. They try to limit coordinated inauthentic behavior even if the content is true and even if the users are "real" people (e.g. workers who are paid to click/promote/create content).
Extremism itself is a vacuous term and normative. Anyone calling for the end of segregation, the end of aparthiad or for gay marriage was once "extremist". So yes it is perfectly A-OK for actual extremists operating under a bare minimium of discretion.
That's a very disingenuous take, but those seem to be the norm for you. People calling for an end to apartheid have not been historically labelled as extremist (other than by apartheid regimes themselves) because apartheid has not been a norm in recent decades, and because the causes you mention all involve the expansion rather than the abridgement of rights, upholding a long-established egalitarian norm.
But to make you happy, I'll qualify my statement, and say that Facebook has been A-Ok with violent and frequently genocidal extremists organizing on its platform.
