He has the rare insight, for a member of his class, that the debate is not about why a healthy and sane globalism is being overtaken by a virulent nationalism. Rather, he says, we have to explain why globalism is attractive to anyone -- it cuts against several very normal moral senses.
It's a good piece, although as usual Haidt strikes me as wrong about some important aspects of things. Still, he is wrong with an open mind that is trying to grasp the other side's position. That's worth something.
Rather than tell you what I think is wrong, though, I'll leave the matter open in case you want to discuss it in the comments.