I always make a point of encouraging people who disagree with me to vote anyway. A point I usually make with this is that there is a strong human bias towards angelizing the guy you are voting for and demonizing the guy you are against, and I make that point when encouraging them. I hope it help them to be epsilon more civil and rational in their future political discussions.

I also imagine that kind of respect for other people's choices keeps my influence on them in the future higher. Who would listen to someone that thinks they are a moron or who has no respect for their values?