Molly Ivins (Lord, how we miss ya) wrote several times that it was the drinking fountains that turned manys of my parent's generation to the left as children--it was so ridiculously, obviously, and demonstrably wrong it just made you think what else where they lying about?
Fifty years and a whole generation later, civil rights still holds that place for me. It's not my only, or even most focused upon issue - the debt, the environment, the war, the rule of law often distract me because they seem so much more emergent. But on just about every other issue I can at least have a debate, a conversation with the other side. What's the proper role and scope of the state, freedom and security, the sanctity of life within certain narrowly defined constraints--I have my own (strongly held) opinions, but I can at least ken where the other side is coming from.