the important thing everyone misses is that these platforms claim protection from liability on what is post because they claim they dont control what users post. So they user the 1st amendment and claim to just be a platform for everyone to speak but then they choose who gets to speak. If the new york times posts a libelous article written by a freelancer they still get sued because they choose to run the article. How is it different with facebook if they are choosing who can be members?