Shouting Fire and Property Rights

A year ago I quoted Murray Rothbard on what he had to say about shouting fire. Sheldon Richman recently argued the same thing, rather conclusively in my opinion:
The "fire in the crowded theater" matter is not an exception to free speech but a recognition of property rights, of which free speech is but a derivative. There's no right to "free speech" on someone else's property. If you buy a theater ticket and then endanger the audience by falsely yelling "fire," you have (among other things) violated the terms of your being in the theater. There's no need to claim an exception to the free-speech doctrine. Properly conceived, free speech is ultimately a property right.