Perhaps my experiences have been worse than usual, but when I make friends with people of a Liberal bent, it doesn't last long. I am conservative, decidedly so. There's not a lot of subjects that I don't bend a bit on, but a couple are pretty concrete, and these always seem to offend people.
Abortion is a good example. Once people find that I am adamantly pro-Life, they seem to have a hard time "agreeing to disagree". I suddenly seem to represent a fascist trying to take people's "rights" away. I'm the kind of person they would hope never, ever had any modicum of power, and who's political activism is seeking to destroy something they apparently hold dear. Understandably, they aren't interested in being friends with someone they consider to be their enemy.
Maybe I have had bad luck, but expecting the Liberals I have tried to befriend to continue an aquaintence seems to be akin to asking them to sit down and have coffee with Stalin. This seems to be made worse by the fact that such people feel it necessary to broach the subject every time they want to have civil conversation with someone. I had one friend for a while that I could see was trying to avoid such topics, but eventually we never seemed to meet up any more.
It goes to deep, maybe. Liberals seem to feel deeply that conservatism is a threat, and that taint seems to stick with me, at least in my experience. I can't imagine what it would have been like to be anti-Nazi in Germany and have to associate with Nazis on a daily basis, but when I sit down to eat with peopel who are pro-Abortion, pro-gun control, anti-war, etc., it actually feels like they think I am some sort of villian trying to destroy their civilization.
I've stopped trying. I either don't talk about politics at all, or avoid people that insist on railing about it in normal conversation. It is next to impossible, though. It seems like "Man, Bush is stupid" is some sort of ice-breaker for Liberals. In order for me to deal with them in real life, I just have to keep my mouth shut.