I am a fan, and his article about nationalism vs. globalism in The American Interest is quite informative. Yet I am disappointed.
Haidt is a man of the left, but has proven to be quite willing to question his own assumptions, and give an opponent a somewhat-even chance. His research, which surprised even him, has been very much of the form "yes, those conservatives do have some irrational responses, but some of them are quite rational that we misunderstand and don't give credit for; and liberals have some irrational thoughts as well, that they turn their heads from and won't acknowledge."
In this essay one can tell that his sympathies lie with the globalist, urbanist, cosmopolitan, and secular values quite reflexively. He thinks those are ultimately the right things, and calls them tolerant, open, and freedom-loving. He does balance this by noting that the nationalist views are not inherently racist, and it is unfair to label them as such, even though real racists can use them to hide behind. He demonstrates a partial understanding of what the nationalist sentiment actually is, rather than what it is sneered to be.
I waited then for the other shoe to drop, which Haidt does quite well, pointing out how current events are also increasing the authoritarianism of the left - in the loss of free speech on campuses where some things may not even be said, and everyone within reach is made to comply with political training; or in the inherent authoritarianism of regulations (showing that it's not an entirely bad thing); or a federal insistence on the narrow range in which your health insurance can be delivered; or how much illegal immigration you will accept, and like it.
That shoe never dropped. Perhaps it is being set up for another essay in follow-up, or is part of a different discussion. Whatever, it's not there now. The essay is valuable. I think conservatives need to contemplate what is happening to them and how their responses may not be as independently conceived as they have assumed. There are parts I thought unfair, but thought I had best at least try and accept, as there seemed to be at least some data behind them. Yet the last third of the essay you will have to write yourself, in your own head, as Haidt hasn't written it.
Update: Grim has also posted and commented on this essay.