It’s not an “error” or an “accident”, as the police now claim. It’s a pattern. First, the Guardian revealed that counter-terrorism police in south-east England have listed Extinction Rebellion (XR) and the youth climate strikes as forms of “ideological extremism”. Then teachers and officials around the country reported that they had been told, in briefings by the anti-radicalisation Prevent programme, to look out for people expressing support for XR and Greenpeace.

Then the Guardian found a Counter Terrorism Policing guide to the signs and symbols used by various groups. Alongside terrorists and violent extremist organisations, the guide listed Greenpeace, XR, People for the Ethical Treatment of Animals, CND, the Socialist party, Stop the War and other peaceful green and left organisations. Then the newspaper discovered that City of London police had listed XR as a “key threat” in its counter-terrorism assessment.

There’s a long history in the UK of attempts to associate peaceful protest with extremism or terrorism. In 2008, for example, the Association of Chief Police Officers (Acpo) produced a list of “domestic extremists”. Among them was Dr Peter Harbour, a retired physicist and university lecturer, who had committed the cardinal sin of marching and petitioning against an attempt by the energy company npower (then RWE npower) to drain a beautiful local lake and fill it with pulverised fly ash. Acpo sought to smear peace campaigners, Greenpeace and Climate Camp with the same charge.

The police have always protected established power against those who challenge it, regardless of the nature of that challenge. And they have long sought to criminalise peaceful dissent. Part of the reason is ideological: illiberal and undemocratic attitudes infest policing in this country. Part of it is empire-building: if police units can convince the government and the media of imminent threats that only they can contain, they can argue for more funding.

But there’s another reason, which is arguably even more dangerous: the nexus of state and corporate power. All over the world, corporate lobbyists seek to brand opponents of their industries as extremists and terrorists, and some governments and police forces are prepared to listen. A recent article in the Intercept seeks to discover why the US Justice Department and the FBI had put much more effort into chasing mythical “ecoterrorists” than pursuing real, far-right terrorism. A former official explained, “You don’t have a bunch of companies coming forward saying ‘I wish you’d do something about these rightwing extremists’.” By contrast, there is constant corporate pressure to “do something” about environmental campaigners and animal rights activists.

We feel this pressure in the UK. In July, the lobby group Policy Exchange published a report claiming that XR is led by dangerous “extremists”. Policy Exchange is an opaque organisation that refuses to disclose its donors. But an investigation by Vice magazine revealed it has received funding from the power company Drax, the trade association Energy UK and the gas companies E.ON and Cadent.

One of the two authors of the Policy Exchange report, Richard Walton, is a former police commander. A report by the Independent Police Complaints Commission said he would have had a misconduct case to answer had he not retired. The case concerned allegations about his role in the spying by undercover police on the family of the murdered black teenager Stephen Lawrence. The purpose of the spying operation, according to one of the police officers involved, was to seek “disinformation” and “dirt” on the family, and stop their campaign for justice “in its tracks.”

The home secretary, Priti Patel, has defended the inclusion of XR on the police list of extremist ideologies. But it seems to me that people like Patel and Walton pose much greater threats to the nation, the state and our welfare than any green campaigners. Before she became an MP, Patel worked for the company Weber Shandwick, as a lobbyist for British American Tobacco (BAT). One of her tasks was to campaign against the EU tobacco control directive, whose purpose was to protect public health. A BAT memo complained that the Weber Shandwick team as a whole “does not actually feel comfortable or happy working for BAT”. But it was pleased to note that two of its members “seem quite relaxed working with us”. One of them was Patel.

In her previous government role, as secretary of state for international development, Patel held unauthorised and undisclosed meetings with Israeli officials, after which she broached the possibility of her department channelling British aid money through the Israeli army, in the occupied Golan Heights. After she was not candid with the prime minister, Theresa May, about further undisclosed meetings, she was forced to resign. But she was reinstated, in a far more powerful role, by Boris Johnson.

Our government is helping propel us towards a catastrophe on a scale humankind has never encountered before: the collapse of our life-support systems. It does so in support of certain ideologies – consumerism, neoliberalism, capitalism – and on behalf of powerful industries. This, apparently, meets the definition of moderation. Seeking to prevent this catastrophe is extremism. If you care about other people, you go on the list. If you couldn’t give a damn about humankind and the rest of life on Earth, the police and the government will leave you alone. You might even be appointed to high office.

It is hard to think of any successful campaign for democracy, justice or human rights that would not now be classed by police forces and the government as an extremist ideology. Without extremists such as Emmeline Pankhurst, who maintained that “the argument of the broken window pane is the most valuable argument in modern politics”, Patel would not be an MP. Only men with a certain amount of property would be permitted to vote. There would be no access to justice, no rights for workers, no defence against hunger and destitution, no weekends.

In his Letter from Birmingham Jail, Martin Luther King Jr, subjected to smears very similar to those now directed against XR and other environmental groups, noted: “The question is not whether we will be extremists, but what kind of extremists we will be. Will we be extremists for hate or for love? Will we be extremists for the preservation of injustice or for the extension of justice?”

Good citizens cannot meekly accept the death of the living planet. If seeking to defend life on Earth defines us as extremists, we have no choice but to own the label. We are extremists for the extension of justice and the perpetuation of life.

• George Monbiot is a Guardian columnist