My own view is confused. I find blanket freedom of speech a mostly libertarian idea that can be criticised on those grounds (cui bono?). And I also find the demarcation of harm at the physical boundary problematic, especially since humans often go to greater trouble to avoid certain kinds of mental harm more than bodily harm. In other words, there are two kinds of arguments I can see that permits these sort of stunts: (a) freedom of individual/speech uber alles. society just cannot morally trample on my right to do anything I want as long as it does not physically harm others, (b) long-term/unknown payoff: this sort of stunt benefits humankind. the trouble with this defence is that some effort, if not complete, has to be made to show how such benefit might accrue.