Professor Katz’ troubles began when he had the temerity to express the wrong opinion: He criticized a campus group, the Black Justice League, in response to a list of racialist demands made during the tumultuous summer of 2020. Before he knew it, his employer was digging through his past, looking for a pretense it could use to terminate him. And, having found what it was looking for in an infraction from 15 years ago, Princeton unceremoniously fired a tenured professor. This is another sad instance of institutions excavating past wrongs to expunge the moral stain of expressing an unorthodox opinion. And it could mark the nadir of free speech on campus.