Seth: I'd rather waste my vote on someone I do support than sell my own values short by voting for someone I don't care about. Caring about something, and sharing that view with others, is the only way to ever change anything.
It's nothing like the war in Iraq because this is something that's in our control. Sure you're single vote won't always matter. But those single votes add up. If everyone who didn't vote in '00 or '04, because they thought their vote didn't matter, would have voted anyway, we would be looking at a different person in the White House.
To say "Nothing you do about politics will change anything, ever," is far more naive than stating what you believe in the form of a vote. Countries are founded and destroyed by people caring about politics. How is that changing nothing?
We are the hungry masses. If we don't let them know it we'll stay hungry forever.