From a libertarian perspective, I would say that the operative principle is ‘My house, my rules’ so that you should be free to say whatever you want on your own property or what other property owners license you to say on their property. Public property, so-called, doesn’t belong to the public but to those who legally control it, usually the local government.
Incitement to violence is often taken to be an obvious limitation to free speech but I don’t think it is. If X incites Y to commit an act of violence and Y commits that act then, unless Y is under some form of mind control by X, Y alone is responsible for his actions. X may be deemed to have some moral responsibility but I cannot see how, in a libertarian world, he could be held legally accountable. The situation is different, however, if the speech in question is the initiation of a joint act.
.
