If I'm a conservative, why are my friends liberal?

As some of you know, I'm politically conservative.  This is fairly meaningless since my interest in politics is much like my interest in professional Starcraft. I'm kinda interested and follow it probably more than is healthy but I don't get particularly fired up about it.

But I do like to debate. I will debate anything, no matter how mind numbing.  I am thinking that this is why I tend to have mostly liberal friends. I enjoy talking to people who disagree with my views more than people who will say "Amen".