Here is one fun way to respond to an anti-gay protester:
Back when I was at Berkeley, there would sometimes be some crazy extremist religious-folk in the central quad area with signs condemning homosexuality. I was walking by them with my (at the time) boyfriend when we decided to hold our own mini counter-protest. I yelled, "hey you religious fuck" to get the wacko's attention, and then me and the boyfriend started making out. We got some nice applause from the assembled Berkeley folk around at the time.