In fact, that’s not what Mortimer Adler said–he said that there were no “Great Books” by black writers before 1955, which was the cutoff date for the “Great Books” series, which was intended to put books that were actually Great in people’s homes.
The problem is that there by definition there are no “Great” books written after 1955, because we won’t know if they’re great for some time, and before that few blacks (and few women–the 1990 revision added Jane Austen) wrote at all. Of course, according to Charles Murray, there may have been few “Great Books” written after 1950, by anyone, but that’s different problem.
Saul Bellow became notorious for having said ”Who is the Tolstoy of the Zulus? The Proust of the Papuans?”, in response to the Western Civ brouhaha at Stanford, which is the assault on “Dead White European Males” that Beam thinks Adler ought to have been paying attention to. This is just common sense, but that one sensible remark is still remembered against Bellow.
And what happens to a professor who isn’t a Nobel Prize winner like Bellow, or an internationally known philosopher like Adler? They get the message and conform, or they get sued.