Generally speaking, if we accept that racism is merely the attribution of race as the determinative factor in describing "human traits and capacities," then I think it's reasonable to think that people can be racist even towards a race to which they belong. But, to be clear, I didn't mean to infer that McWhorter is racist.
I meant only to raise my belief that people sometimes make racist statements that get a pass because those people belong to the race to which the comments are directed. In the case of McWhorter, and let me caution again, I haven't even seen his book, so this is certainly not meant to be conclusive. What made me suspect McWhorter was the brief mention I saw of his discussion on education, and the idea that black people embrace anti-intellectualism. And then I saw a chapter in the table of contents entitled "The Cult of Anti-intellectualism."
So, going back to the above definition of racism, this is an argument where McWhorter might be saying that anti-intellectualism is attributable to race. Again, this is just a guess at what McWhorter's discussion might be. But, if he attributes this "cult of anti-intellectualism" primarily to race, then that's a racist statement, whether or not he is a member of the race to which that statement is directed. As I said, I haven't even seen it yet; but, at first glance, McWhorter's book appears to be the sort of which I am wary.