Just when Labour must have thought the storms had abated and it was safe to go back into the water, the nuclear submarines resurface and all hands brace for impact once again. You almost feel a grudging respect for the party’s endless capacity for self-harm. With the EU referendum reopening deep Tory wounds, here was a chance for Labour to take a refreshing break from smashing one another to pieces and enjoy some skirmishing on the other side.

But not a bit of it. Since Jeremy Corbyn’s election, Parliamentary Labour Party meetings have neatly combined the hysterical screeching of medieval bedlam with the guilty pleasure gawkworthiness of a 19th-century Bavarian travelling freak show. So it was on Monday, when the renewal of Trident enticed various self-dramatising nebbishes – the ones who confuse histrionics with importance – to make a din in inverse proportion to their relevance.

The drama queens’ latest target is Emily Thornberry, the anti-Trident shadow Defence Secretary. She was heckled in a style which reminds me of a night’s professional wrestling at the Albert Hall long ago, when a battalion of white-haired old biddies scuttled in formation to the edge of the ring to wave handbags at Mick McManus.

In defence of these pipsqueak narcissists, Thornberry’s presentation seems to have been no better than on the subsequent morning’s Today programme interview, when she fixated on spurious technological concerns (will underwater drones make it impossible for nuclear subs to hide?) rather than the grand big argument Labour needs to have.

That grand argument is not about the viability of submarines, or whether American approval is required before the launch codes are activated, or the horrendous cost, or how many jobs would be lost were Trident cancelled. It certainly isn’t about whether the absence of Trident would compromise national security. If that were a genuine issue, Hilary Benn, being a humanitarian and a good European, would be leading a “Labour 4 Nukes” coach tour of European capitals. He’d head first to Berlin to explain to Angela Merkel why Germany, as a non-nuclear state, should be quaking in Armageddon’s shadow and begging her to commission a deterrent before Bavaria is turned into a giant radioactive crater.

Mrs Merkel might dredge up some daffy objection to the case made by the de facto president of the Labour’s Trident Fan Club. Something daft about the threat having changed since the Cold War ended a quarter century ago, perhaps. She might even hint at a “nuclear umbrella” meshugas, asking Benn why any hostile power would use the first-strike option knowing the French and Americans are treaty-bound, as Nato allies, to counterstrike and remove that aggressor from the planet? If it’s all the same with you, she might conclude, and thanks a million for popping along, I’d rather spend the hundreds of billions on girly stuff such as schools and hospitals.

Non-nuclear Britain would be just as safe as Germany. That grand argument is all about defining what kind of country we mean to be. For Britain, after all, a nuclear arsenal is not a show of strength. Quite the reverse; it is the clearest imaginable sign of weakness. It’s a huge red arrow pointing at the emasculation of a nation which had its imperial nethers chopped off, and has, ever since, paid way over the odds for a nuclear codpiece to stuff down its knickers to look and feel bigger.

If Corbyn wants a proper debate leading to a clear policy (which he doesn’t, of course; he wants to submerge this problem in meandering debate and eventually find some pitiful fudge), he would ask this: do we want to cling to the decayed edifice of long-lost great power status? Or finally, after decades in denial, embrace our diminishment in the world?

Get rid of Trident and its partner in the struggle for self-delusion, the permanent seat on the security council, would also have to go. Giving the seat away (preferably to India) would be barely less terrible short-term politics than scrapping Trident. The tabloid headlines would be hideous. Nonetheless, the correct long-term decision is to have the Trident fight with Benn and Burnham now because, like the bad general of cliché, they are fighting an old war. It is the war of the 1983 election, in the frozen depths of the Cold War, when a unilateralist manifesto seemed dangerously utopian.

To the new and future voters Corbyn must inspire if Labour is to have a future, spending tens of billions on a uranium-enriched merkin must seem deranged. Their childhoods were free of that recurrent nightmare, when you looked up to see the giant phallus with Cyrillic lettering on its undercarriage bringing the apocalypse at 5,000mph. Since the threat of nuclear attacks means as little to the young as the Empire, they can no more be scaremongered into supporting Trident than tempted to do so by the façade of global importance it confers.

This debate has dribbled on for an entire generation. The absurdity of Trident was neatly satirised 30 years ago in “The Grand Design”, a 1986 episode of Yes, Prime Minister. Sir Humphrey Appleby: Britain should have the best. In the world of the nuclear missile, it [Trident] is the Saville Row suit, the Rolls-Royce Corniche, the Château Lafitte 1945. It is the nuclear missile Harrods would sell you. What more can I say? Jim Hacker: Only that it costs £15bn and we don’t need it.

The times have changed, the cost has increased and the Soviets have vanished. Trident is more unnecessary and less affordable now than then. So let Labour’s zombie narcissists heckle and spit.