Tweet something unwoke and you’ll have your collar felt. Deliberately and determinedly deface a Cambridge college, on the other hand, and the police will stand by and watch. Not only that, they will use emergency powers to divert traffic, giving you a clearer run at your target.

Coppers are human beings, sensitive, like everyone else, to political currents. In the present climate, any infraction of the norms associated with identity politics is considered a heinous offence. Environmentalism, by contrast, is seen as A Good Thing, so we tend to smile indulgently when the more fanatical eco-activists overstep the mark.

When I say “we”, I don’t mean the general population: most people take the sensible view that damaging property is a more serious matter than expressing an opinion. I am referring, rather, to what Antonio Gramsci called the “cultural hegemony”, the dominant ideology as upheld by public intellectuals, broadcasters, politicians, commentators and, these days, actors. It is to their mood, not that of the country at large, that ambitious chief constables defer.

Hence the readiness to see Extinction Rebellion, whose vandalism in Cambridge is just the latest in a series of destructive protests, as well-meaning. Yes, they may go too far, we are supposed to think, and yes, they may technically break the law, but at least their hearts are in the right place.

In fact, Extinction Rebellion is a profoundly illiberal, anti-democratic and misanthropic movement. It displays a disregard for the scientific consensus that would shame even the most extreme climate change sceptic. Its claims are not exaggerations, but inventions. It tells us that “billions will die” of climate change, when not a single scientific body thinks that. It says climate change is causing mass population movements, when the chief causes of migration are economic ambition and political violence.

It says sea-level rises are “unmanageable”, when the IPCC estimate is that they might rise 2ft by 2100 – a problem for some countries, but hardly an unmanageable one. It says “millions are already dying” because of climate-related disasters. Really? In 2019, 11,000 people died from natural disasters. To put that in context, the equivalent figure in 1931, when global population was a quarter of what it is today, was 3.7 million.

We are not dealing with an ecologist movement here, but with something more like a medieval religious cult. The protesters dress in red cowls, smear themselves with blood and shout at every passer-by that the end is nigh, that Judgment Day is coming. These are not people with a reasonable point of view who happen to be expressing it too exuberantly. They are more comparable to, say, the Seekers, the Fifties American sect who believed the world was going to be drowned in a new flood, and that a righteous few would be rescued by a flying saucer.

Such cults should be tolerated, but not humoured. They are free to disseminate whatever crazy ideas they like. But when they act outside the law – gluing themselves to buildings and vehicles, blockading streets, causing criminal damage – they should be treated the same as any other group of yobs who decide to smash things up.

It is worth remembering that Police and Crime Commissioners are there precisely to ensure that the police don’t stray too far from public opinion. The PCC for Cambridgeshire resigned recently after a criminal probe, and his place was filled by his deputy, a Tory councillor called Ray Bisby. Mr Bisby has so far backed his local constabulary, claiming that it was an operational decision, while also saying he understands why there is public anger.​ The public, I suspect, will take a different view. They will understand that allowing, even facilitating, vandalism sends out the worst possible message to potential lawbreakers. If PCCs won't step in in cases like these, what the blithering flip are they for?