Hogwash! It appears that none of those persons took Civics in high school or remembers the content.
The First Amendment limits governmental restrictions on free speech. It says nothing about private restrictions. If someone comes onto my property and paints an objectionable slogan on my house, I have every right to remove the slogan and to order that person not to enter my property again — even if I invited him or her onto my property in the first place. That's an exercise of my lawful rights.
Facebook, Twitter, etc are private enterprises. When you sign up for their services, you are deemed to accept their Terms of Service. Hardly anyone ever reads TOS documents, but you should. The TOS generally gives the service provider every prerogative you can imagine.
Furthermore, you're not paying anything for Facebook, Twitter, etc. Thus there are no consumer protections, no Uniform Commercial Code, or other laws that you could attempt to invoke. (And if there were, you'd face a lengthy court battle against a battalion of smart, well-financed lawyers.)
Lastly, keep in mind that as corporate persons, Facebook and Twitter and the like have their own rights under law. I find it fascinating that the persons who decried the U.S. Supreme Court's opinion in Citizens United — in particular, persons who believe corporations should have no rights — are more than happy for corporations to exercise their rights in this instance.
Do the world a favor, please. If you hear someone complaining about their purported First Amendment rights on social media, please correct them. Gently and respectfully, but firmly.
