I think people are entrenched in their views for the most part, but I don't think it's true that liberals and conservatives don't interact. There are certainly geographic areas where one ideology is dominant, and perhaps in those areas people are less likely to have friends of a different creed. But for most of us, politics just don't reign supreme when picking our friends, neighbors and whom to spend holidays with. Personally--and although I speak for myself I know many people who are the same as me--I'm a fairly liberal thinking I suppose, but my friends and family are all over the map. We talk, argue, debate, but at the end of the day, it doesn't matter if we "compromise" (as the commenter suggests), because there's nothing to compromise over. We aren't the ones making the political decisions. I can convince my gun loving friend that maybe handguns for everyone isn't a good idea, and perhaps he can convince me that we don't need higher taxes, but in the end neither of us has a vote in the legislature. The real problem isn't people not talking, it's political entrenchment (protection of incumbents at all costs to society) and big money politics, where laws are written by groups whom the law is supposed to protect us from.

edit: Friedman is a windbag who just spouts meaningless drivel not supported by data to promote his inane opinions about the world. Not sure how he still has a job, or why anyone listens to him when he's wrong so very, very often.