Dr. Sommers was critiquing campus politics and intersectional feminism, so things were bound to get heated. Issues deserve spirited debate. But baseline hostility to conservative thought makes productive conversation difficult.

Paradoxically, a result of being discouraged from discussing conservatism is that conservatives and libertarians are drawn to more inflammatory figures. Even if we don’t agree with their divisive speech, listening to polemics push back against the endless rules that govern political correctness can be a real relief.

Last spring, I invited Milo Yiannopoulos, the right-wing provocateur, to speak at Bucknell. He was controversial at the time for a flamboyant, over-the-top act in which he said whatever he wanted. There are limits to this shtick: Mr. Yiannopoulos recently resigned from his job as an editor of Breitbart when an ugly joke he made about Catholic priests and young boys was interpreted as an endorsement of pederasty. I am not blind to the concerns over Mr. Yiannopoulos. But there is a reason for his immense popularity as a campus speaker.

Still, because I invited Mr. Yiannopoulos, a professor said publicly that other students at Bucknell should “impose a steep and lasting price” on me and my peers. We were singled out as “racists and fascists,” and I returned to my dorm one evening to find “Tom is a fascist” written on the door. The Bucknell administration was silent.

I understand the irony here. Conservative students criticize the left for seeking protection from ideas they don’t agree with — for defining themselves as victims — and here I am arguing for protection for conservative and libertarian students. But when educators react so violently to ideas and controversy, they shrink the intellectual space of the university environment. They foster an academic atmosphere in which students refuse to question progressive orthodoxy. Worse, some students shy away from asking questions, knowing the social price they might pay.

Political intolerance is hardly confined to one side of the aisle. If conservatives represented the majority of students on campus, I am sure they would be silencing liberals. Universities must push back against the narrowing of ideology generally to guarantee an open intellectual space for all students.

At a time of increased political tension in the country, it is also important for colleges to push students to learn how to grapple with different views. It was Mario Savio, the socialist leader of Berkeley’s free speech movement in the 1960s, who argued that the university should be an intellectual realm where the “hard light of free inquiry” can be brought upon any and all ideas — be they liberal or conservative.