LOL!!! ironically, those are prolly all people what agree with them...
Possibly so. Still, people spend money for tickets to those performances and tend to resent this sort of buffoonery. There should be a uniform plan to counter these protesters wherever they pop up... but it has to be something that both humiliates them and amuses the audience.
Those old-school seltzer bottles might be a good choice (a~la The Three Stooges). Hose 'em down and laugh at them.