Most notably, this occurred at German universities in the wake of Hitler's assumptions of power in 1933. Jews, Socialists, and Communists were massively expelled, and their works were publicly burned.
An infinitely less-destructive time was the McCarthyite era in the United States, when Communism and the Soviet Union became objects of widespread fear and loathing. This had some impact on higher education, where a few academics lost their jobs and a larger number kept their more-controversial thoughts to themselves. It had more visible effects on Hollywood and other corporate employers.
Now we appear to be in a new era of groupthink, where ill-defined terms—racism and sexism, most notably—are the stigmata of choice. This is in good part an accompaniment of the reaction to the Donald Trump presidency. But I think it has deeper roots than that. Its primary advocates are part of a left-wing, anti-American tradition that has long been part of the American intellectual scene. It has gained strength in recent times from fractious but extreme elements of old and new strains of political thought: anarchism, socialism, feminism, black nationalism.
The most conspicuously organized presence on today’s anti-free speech college stage is Antifa, whose expansive definition of who and what is “Nazism” extends to just about everyone to the right of Bernie Sanders. There are other, arguably more important elements fueling the current scene: Trump most notably, but also the inherently hierarchical, predominantly white and still (this is shakier) male makeup of campus faculty and administration. Finally—this is the most slippery, but also may be the most important part of the mix—there is now a student generation raised permissively and seldom challenged in its beliefs, and hence uniquely unready to face the clash of ideas which has always been the theoretical core, but less so the practical reality, of higher education.
This, I think, goes far to account for the current campus tone. (It also suggests that it is likely to fade with a changing political, social, and generational order.) I don't agree that the speaker-disrupters are seeking a debate. They couldn't care less what Charles Murray or other victims of their actions actually have to say about public issues. Like their pro-Nazi and pro-McCarthy counterparts, it is sufficient to declare that the victim is a Jew—or a Communist—or a “racist” or a “sexist.”
Julian Zelizer: My view is that, generally, the state of college campuses is pretty good. When I hear laments about the demise of free speech at universities and colleges, and certainly about the new fascism in university life, my instinct is that these commentators are taking some examples of outlandish protest and crass behavior to paint an inaccurate picture of the majority of students. For instance, the behavior at Middlebury overshadows Murray’s speech at Columbia University soon after, which was uneventful. Murray spoke, people listened, and everyone went home. At my own institution, the debate over whether to rename the Woodrow Wilson School received much more attention than the long list of demands about curriculum and faculty that the students were putting on the table.