Benjamin is not the first to describe this phenomenon. In his 2008 book The Big Sort, journalist Bill Bishop detailed how Americans have been parceling themselves out into increasingly homogeneous communities in which everyone votes for the same political party, goes to the same church and holds the same values.

This situation, Bishop says, has its good and bad points. "The good part is you get this incredible variety from place to place; places zoom off into their own cultural trajectories. But what happens is people lose touch with those who disagree with them. What happens is a nation incapable of compromise; you have this kind of national stalemate."

Ignorance, after all, forms the basis of xenophobia...