A funny thing happened on the way to the revolution. On Saturday, thousands of earnest millennials – and better-humoured Gen-Xers pretending to be millennials – gathered in a field in Somerset for a concert. The headliner was an ancient rocker of an even older tune but the crowd cherished every word as their own – new, meaningful, of the moment.

They cheered. They applauded. They sang this year's secular Te Deum: 'Oh Jeremy Corbyn', wailed to the tune of 'Seven Nation Army' by the White Stripes. And the snake oil flowed. Corbyn, a soft-spoken evangelist, testified and got them raptured up:

“ 'Politics is actually about everyday life. It’s about all of us: what we dream, what we want, what we achieve and what we want for everybody else. The commentariat got it wrong, the elites got it wrong. Politics is about the lives of all of us. The wonderful campaign I was a part of and led, brought people back to politics because they believed there was something on offer for them.'

They ululated their devotion and their shambling prophet beheld his fervid, nescient apostles. They are not fanatics, they protest, but fed up. They want change, rid of the Tories, a future for themselves. They are not seeking faith but hope. And yet here they are hollering their approval for a veteran Eurosceptic, a career politician committed to withdrawing from the EU, leaving the single market and ending freedom of movement. You cannot engage someone coming to Jesus on the physics of walking on water. They want Corbyn because he is honest and principled and will put an end to austerity. When George Osborne announced a further £9bn cuts to welfare in 2015, the Labour front bench ordered MPs to abstain. Corbyn rebelled and parlayed anger at the compromise into backing for his leadership campaign. Now he is committed to implementing £7bn of those very same cuts if he reaches Number 10. These are facts, but proof is no longer sufficient or relevant. No talking in church.

This same joyful credulity immunised the young from revulsion at Corbyn's extreme views and associations. Corbynistas trill with unseemly glee that no one cares about the IRA or anti-Semitism. Well, I care. I care that people don’t care. I care that a party I would like to be able to vote for is a furious foe of every brand of racism except one. I care that the historical record on the Troubles can be revised by ignorance and excused by those who know better simply because it is politically advantageous. I care because the margins are overcoming the mainstream. If a Tory MP declared tomorrow that Enoch Powell was instrumental in passing the Race Relations Act, that the Rivers of Blood speech was an effort to reach out to racists and win them round to the cause of ethnic harmony, who in the Labour Party could raise an objection?

Labour has moved to the left and ended up on the right – hard Brexit, controls on immigration, slashing benefits. The author of this policy shift, at least as dramatic as any performed by New Labour, was hymned by the Glastonbury faithful as a man of conviction. The Conservative Party may be in crisis but conservatism is in safe hands. True believers – joined of late by many converts – dismiss centrists as out of touch, soon to be left behind in the march to victory and vindication. If revisionism is progress and anti-Semitism irrelevant, I no longer seek progress or relevance. If the price of a Labour government is membership of this cult of anti-knowledge, it is a price too high. I want to be left behind.