A woman passes a tent encampment set up by student protesters following an announcement that University of Missouri System President Tim Wolfe is resigning Monday, Nov. 9, 2015, at the university in Columbia, Mo. (Jeff Roberson/AP)

NOWHERE BETTER epitomizes the open debate and free expression that are such cherished parts of American academia — and American life — than the campus quad. So the sight of protesters at the University of Missouri harassing and blocking journalists was startling, to say the least. The incident was especially troubling since a rising tide of student activism, admirable in many respects, seems increasingly infected by a strain of intolerance of dissenting views.

“Hey hey, ho ho, reporters have got to go” was the chant Monday as protesters surrounded and harangued Tim Tai, a student photographer on assignment for ESPN. Mr. Tai was trying to chronicle the protests of alleged racism that forced the resignation of two top university officials. “This is the First Amendment that protects your right to stand here and mine. . . . The law protects both of us,” said Mr. Tai as he tried to reason with the crowd. Incredibly, among those trying to bully Mr. Tai were university staff members. As another student videoed the events, an assistant professor of mass media (no, we are not making that up) asked, “Who wants to help me get this reporter out of here? I need some muscle over here.”

No one has been able to explain how the media — earlier sought out by protesters wanting to publicize their complaints — became the enemy. But it was clear from the video , which went viral, that at least some students believed that their rights and views should trump the rights and views of others. Similar disturbing behavior was on display in another recent video, also gone viral, of college students exercising their rights. This time the scene was Yale University, where a professor was shouted down and bullied as he tried to express his views about a controversial e-mail written by his wife, a lecturer at Yale. Among the insults hurled at him: “You should not sleep at night! You are disgusting.” And “Walk away, he doesn’t deserve to be listened to.” Punishing dissent became far more than just a threat when the student government at Wesleyan University last month voted to cut funding for the 150-year-old campus newspaper because it had the temerity to publish an opinion piece by a conservative writer questioning the tactics (but not the message) of the Black Lives Matter movement.

The spark for student action in these cases was allegations of racial bias and institutional insensitivity, serious concerns that should be taken seriously by the larger public as well as by university administrators. Good for students for speaking up and urging action when they see unfairness. But in not respecting — in attacking, even — the free speech of others, they undermine the cause of acceptance and tolerance. That runs the risk of making universities a place not of learning but of conforming.