People generally can't stand to have their views challenged, and when they can they refuse to engage in intelligent discussion that may result in compromise, or at least a deeper understanding of the other side. It's becoming increasingly rarer for people to engage in meaningful discussion about nearly any hot topic.
Instead, everyone who agrees with them is smart, and everyone else are a bunch of retarded brainwashed sheeple who need to wake up. Or whatever buzzphrase they can think of.