Why hate someone because they have a different political view?

I have been called both a Liberal Democrat and a Conservative Republican by people on and off this website. To be honest I don’t consider myself either. I vote for the individual instead of the party. I agree with many things the Republicans have to say, but I think that Democrats also have a lot of good ideas. I think that debate and disagreement is a natural part of politics, however some people profess hatred for someone that does not have a similar view. I don't believe the majority of Liberal Democrats are lazy people living off of the system and I don't believe most Conservative Republicans are greedy elitists. Let me know if you agree/disagree.