[cosmiccartel]

You're confusing the First Amendment with the principle of Free Speech.

When it comes to privately owned forums, they may have absolute control over what is acceptable to say, but those who disagree with their policies are perfectly justified in criticizing them for violating the principle of free speech.

But it isn't even as black and white as you say from a legal standpoint. There is precedent (Marsh v. Alabama) for the owners of a publicly-used, privately-owned space to have their rights limited in order to protect the constitutional rights of persons using the space. The same principle could apply to sites as large as Facebook, Twitter, or Reddit.