1)Does Facebook have the constitutional right to deny someone fro

1)Does Facebook have the constitutional right to deny someone from posting information on a public forum if it is not obscene?2)Who gets to decide if a claim is actually fraudulent?  What if a scientist has made a discovery, that is unknown to other scientists, that reduces the symptoms of the virus?  Should Facebook have the right to deny publication because the treatment has not been publicized?3)Obviously, Facebook has the right to deny publication of information that is obscene or dangerous.  What are some other reasons that would give Facebook the right to refuse to publish information?