From Mark Lilla in the New York Times:

Finally, the whitelash thesis is convenient because it absolves liberals of not recognizing how their own obsession with diversity has encouraged white, rural, religious Americans to think of themselves as a disadvantaged group whose identity is being threatened or ignored. Such people are not actually reacting against the reality of our diverse America (they tend, after all, to live in homogeneous areas of the country). But they are reacting against the omnipresent rhetoric of identity, which is what they mean by “political correctness.” Liberals should bear in mind that the first identity movement in American politics was the Ku Klux Klan, which still exists. Those who play the identity game should be prepared to lose it.