The abuser has as much a right to be there as I do, but I disagree they have a right to act in a clearly harassing/heckling manner. If they have something important to say that's worth protecting with free speech laws, that's not the way to say it. If that's the sort of behaviour that's protected by the 1st amendment in the US, you're welcome to it. On the other hand, nor do I ever wish to live in a country that criminalises criticism of anyone, esp. those in positions of power.