Some thoughts to accompany my report and pix of the 2010 Comic-Con--specifically the anti-gay protest:
When comic-book nerds support gay rights, you can believe the issue has gone mainstream. That makes it safe for others to think and say, "You know, maybe gays really are harmless. Maybe it's okay to let them marry."
This is one way protests influence public opinion: by moving the needle on what's acceptable or unacceptable. Claim that "fags are beasts" and hundreds of normal people will shout you down. You can rethink your position or become a reviled outcast...your choice.
The same thing happens with protests against racism and stereotyping. If you protest often enough and get enough people behind you, it'll shift the needle on the acceptability of these things. Beliefs and expressions that were acceptable won't be any longer.
For more on particular protests, see:
Asians protest Last Airbender
Zazzle's "Indian name" t-shirts
Natives lead Arizona law protest
Anti-Dudesons protest at MTV Awards
For more on protests in general, see:
Indians shouldn't act uppity?
Do protests work?
Protesting stereotypes = cop-out?