Keeping your bar from becoming a nazi bar doesn't *only* mean kicking out the nazis that show up to drink and party.
It means making sure a rich nazi just doesn't straight up buy it and become the new boss regardless of what anyone else thinks.
It means making sure your locksmith, bouncer, structure itself isn't giving nazis means of entry where they can get one in, then another, then another until the whole mob is in.
It means making sure the land the bar's on isn't owned by a rich nazi.
Defense in depth.
And letting Facebook in is essentially breaching all the defenses, *especially* if they can buy a controlling interest/close the activitypub ecosystem/spam rush every site, etc.