Jeremy Hunt does not come across as a man much burdened by the need to believe things with consistency. The foreign secretary rose to cabinet rank under David Cameron and wears his Conservatism in the style of that era: casually, with a liberal streak on top and not much underneath. He backed membership of the European Union in 2016, but had a change of heart last year. This was provoked, Hunt said, by exposure to “the arrogance of the European Commission”. The requirements of Euroscepticism in any aspiring Tory leadership candidate may also have featured in his journey.

But admission to the club of Brexit believers is not easily won. Last week, Hunt upset Conservative backbenchers by saying that failure to strike a deal with the EU “would be a mistake we would regret for generations”. This statement was only remarkable because it was true. The foreign secretary quickly fixed that. Of course Britain would prosper in a no-deal scenario, he clarified with a cringe. The mistake would be Europe’s, as would the regret.

A revealing feature of that episode was the Brexit fundamentalists’ refusal to recognise the foreign secretary’s conversion to their creed. “We don’t need any lectures from remainers,” said Nigel Evans, a Tory MP associated with Leave Means Leave – a campaign group that dissolves the boundary between the Conservative party and a harder rightwing fringe.

The bullying of Hunt contains a challenge to those Tories who voted remain, but accept the referendum result and hope to find a sensible way to fulfil the mandate. It is a warning to those who just want to say it has been done and move on. The message is that Brexit is not that kind of project at all. It is not an agenda that can be adopted pragmatically because pragmatism runs against the spirit of the thing. Pragmatists like Hunt expose themselves as unbelievers. They accept Brexit with their heads, but they haven’t accepted it into their hearts. A majority of Tory MPs fail this test. Before the referendum, most were Eurosceptic in a loose, cultural sense. That was usually a condition of their selection as parliamentary candidates. A little Brussels-bashing over dinner was reflex and routine. But few considered how Britain might actually sever the ties, nor what it might cost. When they did, most saw that it wasn’t worth it.

Theresa May was in that category once, and the Brexit thought police will not let her forget it. From her first day in Downing Street she has felt the need to scrub away the stain of her remain vote. That is how she ended up negotiating from behind impossibly restrictive red lines. The prime minister’s commitment to take the UK out of the EU is proven beyond reasonable doubt. Yet it is a racing certainty that Jacob Rees-Mogg and his acolytes will one day declare that the milk and honey can’t flow because May’s faith was not strong enough. They will say that deep down, in her traitor’s heart, she was a remainer all along.

Still many Tories believe their party can avoid a civil war. One model, privately discussed among MPs, involves bundling Britain over the Brexit finish line next March with a sketchy, provisional deal, based on May’s Chequers blueprint. The details can then be finessed in transition. This position is often associated with Michael Gove, who has not so much softened his Brexit theology as adapted it to the available implementation timetable. The idea is to make sure the legal bridges back to EU membership are burned on time. Then most people will lose interest, May can be thrown under a bus and the real work of disentanglement can proceed under a new leader.

The potential appeal to hardliners is that this plan minimises the risk of an autumn crisis so vast that somewhere in the melee, Brexit is lost altogether. The appeal to the rest of the party is that it opens a window onto a world where they don’t have to talk about the EU any more. That is also a popular proposition beyond Westminster.

But the Tory pragmatists are wrong to imagine thattheir agonies end and healing begins after Brexit. It is clear already from the rhetoric and behaviour of the radical leavers that getting out of the EU is barely the start. They are facing a culture war against liberalism and the pre-2016 norms of British democracy. Leave.EU, Nigel Farage’s referendum campaign vehicle, has morphed into an engine of generalised Trumpian malevolence and is encouraging supporters to join the Conservatives. Some Tories report the return of racists and cranks who stormed out over gay marriage five years ago. Conservative membership is around 120,000. The number of energetic activists is much lower. In many areas it is a frail shell, easily requisitioned by entryists.

There are MPs who put their faith in a silent, sensible majority; a hidden ballast ofstalwart, no-nonsense, old-fashioned Tories who might have reactionary views on social issues but who take their civic duties seriously and recoil from actual fascists. This bedrock of respectability is supposed to uphold the cause of pragmatism in any leadership contest. The danger is that this cohort is quiet not because that is their style, but because they aren’t there any more. If this sounds familiar it is because Conservative moderates are saying many of the same things that Labour MPs said when first confronted with Jeremy Corbyn’s leadership bid. Liberal Tories watched with condescending pity as their opposition counterparts were humiliated by a radical movement beyond parliament’s walls. They believed in British Conservatism’s immunity to capture by ideological extremes, even as they felt the tremors beneath their own benches. They fretted about Faragism in their midst but saw it as a passing storm, after which they might get their party back.

They must now realise that nothing is just going to default back to the way it was. The options for reviving a liberal, one-nation school of Toryism are to fight the extremist takeover, or carry the flame elsewhere to a different party. Sitting tight, waiting until “after Brexit”, is an act of intellectual surrender amounting to political suicide. There is no “after Brexit” because the revolution can never be finished; the old order cannot be allowed to survive. Nationalist vultures are already circling over the limp, motionless body of Tory moderation. If it doesn’t rouse itself and show some life, it will be picked to pieces.

• Rafael Behr is a Guardian columnist