Why is there so much hatred between Republicans and Democrats?

Basically Republicans don't want to actually debate the issues because 1. The facts are not on their side. 2. They are smart enough to know that most Americans are bored by policy discussions anyway. So instead they just exaggerate and make stuff up: "Obama is going to kill your grandma with death panels!" Obviously Republicans who believe this nonsense are going to hate Obama and everyone who supports him. Who wouldn't hate someone that was trying to kill your grandma?