As supporters of Jeremy Corbyn read the Observer, could the rest of you talk among yourselves while I speak to them directly?

You should know there is a faint chance Theresa May will call an early election. She says she doesn’t want to, and it would be difficult to arrange. But May also said she didn’t want Britain to leave the European Union, and look where we are now. Perhaps Channel 4’s exemplary investigation into Tory campaign expenses will force so many byelections, May will think, “What the hell, let’s go the whole hog.” Perhaps she will say she is an unelected prime minister who needs a personal mandate to govern and a political mandate for her version of Brexit.

Do you still believe the far-left politicians and journalists who promised that you would have shifted “the Overton window” by now? This cod piece of jargon, purportedly describing how political discourse changes, came from the American right. Appropriately enough, you might think, because far from building a new consensus for previously unthinkable leftist ideas, Corbyn’s victory has allowed the right to run riot. I won’t insult your intelligence by asking whether you also believe the bullshit you were fed about a “genuinely radical” Labour party attracting people who did not vote to turn out for him. There was never any evidence that they were secret socialists. I understand, too, that it would be cruel now to drag up the old boasts about how the left would win back Scottish nationalists now that Corbyn is so unpopular even Scottish Tories can walk all over him.

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Still, you should not forget that those boasts were made, and that bullshit was fed to you.

On current polling, Labour will get around a quarter of the vote. Imagine, though, how the Labour party will fare in an election campaign when its leaders are Corbyn, John McDonnell, Emily Thornberry and Diane Abbott, and its second XI consists of Clive Lewis, Angela Rayner, Richard Burgon and Rebecca Long-Bailey. The Tories have gone easy on Corbyn and his comrades to date for the transparently obvious reason that they want to keep them in charge of Labour.

In an election, they would tear them to pieces. They will expose the far left’s record of excusing the imperialism of Vladimir Putin’s gangster state , the oppressors of women and murderers of gays in Iran, the IRA, and every variety of inquisitorial and homicidal Islamist movement, while presenting itself with hypocritical piety as a moral force. Will there be 150, 125, 100 Labour MPs by the end of the flaying? My advice is to think of a number then halve it.

One senior Labour figure told me he thought Corbyn was endangering British democracy. It depends on the opposition being a government-in-waiting. Labour looks now as if it will never be in government again. The 60% of the population who do not want Conservative rule are faced with Conservative rule without end, with the only pressure for change coming from an ever-more audacious right.

More troubling for you ought to be the question why might May, a prime minister with a fragile majority, not bother to call an early election. One cabinet minister explains her insouciance thus.

He and George Osborne used to worry about how Ed Balls and Chuka Umunna would strike back against their austerity programme. Now ministers do not give Labour a second’s thought. It ought to shame you to learn that, ever since Corbyn promised to take the fight to the Tories, he and his hopeless frontbench have not forced one Tory minister to resign or even endure a sleepless night. The budget fiasco was exposed by journalists and Tories. Despite their help, Corbyn could not land a slap on May’s wrist let alone a punch. His feebleness was just an appetiser.

Labour politicians who want to fight rather than pose say they can see the right mobilising to demand the worst possible Brexit. Britain should defy the EU and pay nothing or next to nothing towards the divorce bill, it will say.

May has never once dared cross the Daily Mail. She will agree that “no deal is better than a bad deal” and push us over a cliff with only the hope that we can become a low-tax, low-regulation utopia as a parachute.

Is that your utopia? A Britain you would be happy to live in? (I assume, incidentally, that there will still be a Britain, even though I cannot see how the derided Corbyn can persuade the Scots to stay in the union any more than he could persuade the rest of the country to stay in the EU.)

I don’t mean to mock you when I say that you think of yourselves as blameless people. I just want to warn you that you will be blamed for the poverty and chaos that is coming.

In 1968, when Robert Conquest published The Great Terror, his account of the vast crimes of Soviet communism, leftwing critics accused him of being a cold war warrior who exaggerated to further Nato’s cause. As the truth of his work became undeniable, Conquest’s friend Kingsley Amis said he should celebrate his book’s vindication by changing its title. As The Great Terror was a fine title, Conquest asked, what could be possibly top it?

“I Told You So You Fucking Fools!”

The same words will be flung at you by everyone who warned that Corbyn’s victory would lead to a historic defeat.

I accept that among you there are true far leftists who won’t care. You want, and may get, a “radical” Labour party that will spend decades in opposition waiting for the glorious day when voters realise their mistake.

I don’t think your imaginary victory is worth waiting for. You don’t have a radical programme that a 20th-century Marxist or any other serious thinker would recognise. All that’s left of the far left is a babble of sneers and slogans. But, let me be fair, by your own lights you have a strategy, and are not complete fools.

The majority of Corbyn supporters are another matter. Labour MPs are biting their tongues now and letting Corbyn show himself for what he is.

Next year, as austerity grinds on, as we crash out of the EU to find ourselves with Donald Trump as our last ally, they will run candidates against Corbyn and ask for your support. That will be the moment when you need to look at your country and ask whether this was what you wanted when you first cheered “Jeremy” on.

In my respectful opinion, your only honourable response will be to stop being a fucking fool by changing your fucking mind.

• This article is the subject of a column by the readers’ editor