In an appearance on the Charlie Rose TV show Haidt had this to say (from the transcript):

Mark Lilla had a piece in “The New York Times” right after the election on the problem of identity politics and how this may have alienated a lot of people and contributed to Trump’s victory. And the response from many academics was ferocious. One of his colleagues at Columbia, within a few days, had some essay basically linking him to the Ku Klux Klan. But here is the point. So Lilla comes back with this brilliant point. He says, that’s a slur, not an argument. And once he said that, I realized oh my God, that is exactly what has been happening to me. I’ve been saying some pretty provocative things beginning with an Atlantic article with Greg Lukianoff, and I keep looking on the internet for people who will respond to it. And pretty much nobody is — nobody is arguing against me for anything I say, but I do get a lot of people basically saying, I am a white male or I somehow I am winking at racism, something like that. So, young people who go through these colleges, they’re exposed to rhetorical training that prevents them from learning how to engage. They are trained carefully in how to basically discredit your opponent. Slur, they learn to slur. They do not learn to argue.