Amy Wax, a tenured professor at the University of Pennsylvania Law School, was recently barred from teaching certain courses there. Her crime? During an interview in September with Glenn Loury, a black economist at Brown University, Ms. Wax remarked on the academic underperformance of black students at Penn Law.

“Here’s a very inconvenient fact, Glenn: I don’t think I’ve ever seen a black student graduate in the top quarter of the class, and rarely, rarely, in the top half,” said Ms. Wax. “I can think of one or two students...