SCOTUS decision in 1946 (Marsh v Alabama) said free speech couldn’t be limited in “public square” even if the public square was privately owned.
The proprietor of a social media business is the gatekeeper. Free Republic operates in a similar fashion. It has published the rules for engagement. If the moderator decides, an active member can be zotted without recourse, because it is not PUBLIC.
Get with it, my FRiend.