Free Speech and the First Amendment

The free speech clause of the First Amendment to the United States Constitution protects the citizen's right to free expression from infringement by the government, not from infringement by any old entity.  My home is my castle; you have no First Amendment rights here, or at my cyber-castle, my weblog. So it is no violation of your First Amendment rights if I order you off of my property because of your offensive speech or block you from leaving stupid or vile comments at my website. It is impossible in principle for me to violate your First Amendment rights: I am not the government or an agent thereof.  And the same holds at your (private) place of work: you have no First Amendment rights there.