The movement for free speech on campus was born at the University of California, Berkeley in 1964. Last night it died there. In the intolerant screams, smashed glass and fire — actual fire — of the Berkeley protesters who successfully prevented Milo Yiannopoulos from speaking, the ideal of free speech on campus was dealt a fatal blow. It’s undeniable now: the modern western university, once a bastion of thought experimentation, is now one of the most hostile places on earth to freedom of speech and robust debate.

It’s tempting simply to ridicule the students and anarchists who gathered in vast numbers in Berkeley last night to insist that Breitbart provocateur and Trump fanboy Milo be thrown off campus. It’s tempting to hurl the usual epithets: they’re snowflakes, wimps, typical touchy millennials. But that isn’t enough. It doesn’t cover it anymore. The Berkeley fury confirms we face something far worse than spoilt yoof acting up. This was a positively pre-modern outburst; a mob; an ugly, irrational use of force and fire to prevent the expression of ideas. Future historians will study this, surely, and wonder how such censorious hysteria came to take hold of the leading academic institutions of the west.

The scenes at Berkeley were truly unnerving. Protesters, a mix of students and non-student anarchists who turned up for an anti-Trump ruck, yelled and stomped and set off fireworks. They smashed the windows of the building in which Milo was due to speak. They started a fire, near the campus bookstore, fittingly: after all, it’s a thin line indeed between using fireworks and fury to silence controversial speakers and burning books. ‘This is war’, one banner said. Yes, it is: it’s a war on freedom, on rational debate, on the very values of tolerance and discussion that make university life possible in the first place. Berkeley management called off Milo’s talk. Today, President Trump tweeted about it: maybe Berkeley should be denied federal funds, he said, if it won't 'allow free speech'.

This behaviour would be shocking on any campus, but at Berkeley it’s especially tragic. This is the university where, in 1964 and 1965, students agitated for freedom of speech. The Free Speech Movement staged sit-ins and protests demanding that university management lift restrictions on inviting outside political speakers and on students and staff advocating for political causes. Students fought for their right to invite to ‘controversial’ people, including Communists, and to express their political feelings. Now, in one of the saddest and most striking volte-faces of modern times, Berkeley students do the opposite: they fight, hard, to restrict freedom of speech; they demand the expulsion of outside speakers; they call on the university to silence people in order to protect students’ self-esteem.

So last night’s mad, mob-like behaviour at Berkeley tells us a bigger story about the 21st century. It speaks to a shift from earlier generations that wanted to be treated as adults, as free, political creatures, to a new generation that wants to be infantilised, and which infantilises itself in fact, seemingly not trusting itself to be fully adult. ‘Give us freedom!’, cried the student radicals of the 1960s. ‘Protect us!’, cry so-called student radicals today. Earlier radicals wanted to break free of the rules of in loco parentis and be autonomous; today’s campus agitators want to hide in the Safe Space, withdraw from the adult, political world of debate and confrontation, and be cared for, forever.

What happened at Berkeley was horrendous, but it was also only a more extreme expression of what has tragically become a mainstream idea: that it’s acceptable to curtail free speech in the name of protecting people’s feelings. We see this everywhere now, from the NUS’s 'No Platforming' of hard-right speakers to student unions banning the Sun to the fire and broken glass at Berkeley. There is a continuum between the polite NUS policy saying ‘End Lad Culture’ and the starting of a fire to stop Milo from speaking: both speak to a terrifying new intolerance, to the tyrannical elevation of some individuals’ self-esteem over everyone else’s right to think and say whatever they please.

When literal fires of censorship can be started at one of America’s most prestigious universities, we know we have a serious problem on our hands. This goes beyond snowflakes and millennials. Enlightenment thinking itself seems to be in disarray, in particular the Enlightenment ideals of freedom and tolerance. The only sane response to what happened at Berkeley is to get serious about freedom of speech, and remind people that their feelings must always take second place — a very far second place — to the principle of free speech for all.