I have had it up to here with the Conservative party. Not, perhaps, an unusual sentiment to find expressed in the Guardian. But, as a centre-right columnist, I do not start from the proposition that all Tories are inherently evil champions of “neoliberalism” (whatever that means), intent on maximising suffering and despair. I don’t express this contempt for the party blithely or to prove a point. This is not an exercise in rhetoric. I mean it.

By way of explanation: I used to edit the Spectator. I am proud to chair a centre-right thinktank, Bright Blue. I wrote a book about the Conservative-led coalition. And if you think that’s bad, I was one of the few people in the world who applauded aspects of Theresa May’s 2017 manifesto (that’s a really select club).

True, I have never been a Conservative member – on the whole, I don’t think journalists should join parties, though many excellent ones do so. But, as a believer in fiscal discipline, strong defence, robust anti-terrorism measures, the Atlantic alliance and the social liberalism of those who live in the here and now, I ought to be at ease with modern Conservatism. And I really am not. Brexit has tested that broad affinity to destruction – and in this respect I know that I speak for many on the centre-right.

Yes, Jeremy Corbyn’s vacillation has been pathetic. But he is the leader of the opposition. It was a Conservative government that called the referendum, and a Conservative prime minister who – having squandered her party’s majority in the 2017 general election – bought the support of the Democratic Unionist party with taxpayers’ money so she could stay in power and finish the job. Brexit is a Tory gig.

And it has brought out the very, very worst in the party. The attack on “Teutonic arrogance” by Mark Francois MP – in response to the warning by Airbus boss Tom Enders of the consequences of a no-deal withdrawal – would be easy to dismiss were it not the tip of a nativist iceberg.

It is uniquely dispiriting to see intelligent Conservatives cheerleading or appeasing this drive towards disaster

Brexit has summoned the very worst demons that lurk in the Conservative psyche, liberating Tories to bellow nonsense about the second world war, the blitz spirit and pseudo-Churchillian defiance. It has fatally compounded the party’s demented fixation with immigration and distracted it from the true challenges of the 21st century.

Parliament used to be the crucible of the Conservative ethos: the place where history met contemporary discourse. Now, we have MP Jacob Rees-Mogg – a man still spoken of by supposedly serious colleagues as a leadership contender – urging Theresa May to suspend the legislature if it seeks to thwart a no-deal Brexit.

In the cabinet, we have the trade secretary, Liam Fox, saying that government can be the servant of the people or the servant of parliament, but it cannot be both. A chilling populism is now creeping into the language of mainstream Toryism: the language of treachery, snarling tribalism and impatience with anything that smacks of prudence, compromise or caution. In the Conservative stockade, emotion has toppled fact.

This, in the end, is the unforgivable act of intellectual surrender. By tradition, the strongest claim the Tories have had to office is a belief that ideology should be subordinated to reality. Even Margaret Thatcher – the most explicitly ideological of Conservative prime ministers – was ousted to stop the poll tax and to salvage Britain’s relations with Europe.

As Michael Portillo put it a few months after he had lost his seat in 1997: “It is extremely important for the Conservative party to deal with the world as it now is.” This was the animating idea behind what became Tory modernisation and the basis of David Cameron’s leadership campaign in 2005: the notion that a centre-right party should, on principle, celebrate the diversity of contemporary life and the plurality of modern society. Alas, that project – which reached its high point in Cameron’s legislation for marriage equality in 2013 – now lies in ashes.

The whole point of Conservatism is not to submit to the siren call of teleology: the belief that history has an implacable direction. In a crisis of this nature, the proper role of Tories should be to cut through the infantile rhetoric, robotic platitudes and Vogon insistence that “resistance is useless!”, and show true statesmanship. Instead, we see – with some outstanding exceptions – a party cravenly fetishising the 2016 referendum as if no further expression of popular opinion on Brexit were possible; behaving as if the only thing that matters is to get out of the EU by 29 March, regardless of the overwhelming empirical evidence that there is no viable deal, and that a no-deal exit would be a total catastrophe (necessitating, among many other unpleasant measures, a framework for martial law).

Look at them all: fiddling with the backstop while the treaty of Rome burns (or at least the page that bears Edward Heath’s signature). It is uniquely dispiriting to see intelligent Conservatives cheerleading or appeasing this drive towards disaster.

Politicians always tell me that the demands of the life are worth it because of the agency you get to exercise. Well, where is that agency right now? Where are the Tories prepared to risk their careers and to say that the instruction given by the electorate in 2016 cannot be delivered in a way that does not do terrible harm to those same voters and their children?

To be clear: I haven’t undergone a conversion. My values have not changed. But the Conservative party is morphing into something I find alien and repellent. Like a listing galleon, holed below the waterline, it sails away stubbornly; dragging the nation towards a storm of unknown adversity, peril and pain.

• Matthew d’Ancona is a Guardian columnist