HALLOWEEN is supposed to last for one night only. At Yale University (motto: “Light and Truth”) it has dragged on considerably longer. As happens at many American universities, Yale administrators sent an advisory e-mail to students before the big night, requesting them to refrain from wearing costumes that other students might find offensive. Given that it is legal for 18-year-old Americans to drive, marry and, in most places, own firearms, it might seem reasonable to let students make their own decisions about dressing-up—and to face the consequences when photographs of them disguised as Osama bin Laden can forever be found on Facebook or Instagram. Yet a determination to treat adults as children is becoming a feature of life on campus, and not just in America. Strangely, some of the most enthusiastic supporters of this development are the students themselves.

In response to the Yale e-mail, a faculty member wrote a carefully worded reply. In it she suggested that students and faculty ought to ponder whether a university should seek to control the behaviour of students in this way. Yes it should, came the reply, in the form of a letter signed by hundreds of students, protests and calls for two academics to resign for suggesting otherwise. Tellingly, the complaint made by some students at Yale’s Silliman College, where the row took place, was that they now felt unsafe.

On the face of it this is odd. New Haven, which surrounds Yale, had 60 shootings in 2014, 12 of them fatal. Thankfully, there has never been a shooting at the university. The choice of words was deliberate, though. Last year a debate on abortion at Oxford University was cancelled after some students complained that hearing the views of anti-abortionists would make them feel unsafe. Many British universities now provide “safe spaces” for students to protect them from views which they might find objectionable. Sometimes demands for safe space enter the classroom. Jeannie Suk, a Harvard law professor, has written about how students there tried to dissuade her from discussing rape in class when teaching the law on domestic violence, lest it trigger traumatic memories.

Bodies upon the gears

Like many bad ideas, the notion of safe spaces at universities has its roots in a good one. Gay people once used the term to refer to bars and clubs where they could gather without fear, at a time when many states still had laws against sodomy.

In the worst cases, though, an idea that began by denoting a place where people could assemble without being prosecuted has been reinvented by students to serve as a justification for shutting out ideas. At Colorado College, safety has been invoked by a student group to prevent the screening of a film celebrating the Stonewall riots which downplays the role of minorities in the gay-rights movement. The same reasoning has led some students to request warnings before colleges expose them to literature that deals with racism and violence. People as different as Condoleezza Rice, a former secretary of state, and Bill Maher, a satirist, have been dissuaded from giving speeches on campuses, sometimes on grounds of safety.

What makes this so objectionable is that there are plenty of things on American campuses that really do warrant censure from the university. Administrators at the University of Oklahoma managed not to notice that one of its fraternities, Sigma Alpha Epsilon, had cheerily sung a song about hanging black people from a tree for years, until a video of them doing so appeared on the internet. At the University of Missouri, whose president resigned on November 9th, administrators did a poor job of responding to complaints of unacceptable behaviour on campus—which included the scattering of balls of cotton about the place, as a put-down to black students, and the smearing of faeces in the shape of a swastika in a bathroom.

Distinguishing between this sort of thing and obnoxious Halloween costumes ought not to be a difficult task. But by equating smaller ills with bigger ones, students and universities have made it harder, and diminished worthwhile protests in the process. The University of Missouri episode shows how damaging this confusion can be: some activists tried to prevent the college’s own newspaper from covering their demonstration, claiming that to do so would have endangered their safe space, thereby rendering a reasonable protest absurd.

Fifty years ago student radicals agitated for academic freedom and the right to engage in political activities on campus. Now some of their successors are campaigning for censorship and increased policing by universities of student activities. The supporters of these ideas on campus are usually described as radicals. They are, in fact, the opposite.