Each side is so entrenched in their beliefs. Conservatives think liberals are psychotic hypocritical, immune to facts idiots who are brainwashed. And guess what? Liberals think that about conservatives. If you can't find shortfalls in your own belief system and can't concede you don't know everything and are not solely right on every issue, then you're falling into the same trap you are accusing liberals of. For every specific instance of a liberal saying something stupid like Jim Carrey, there is a conservative doing the same thing.
Remember when people were smashing their Keurigs, because they pulled ads from Sean Hannity?