It brings a tear to the eye. The old times we never thought to see again are back. The talk is of hard left and soft right, of Trots, Bolsheviks and revisionists. Where were you, goes the clever question, not at Marston Moor but at Kronstadt? Where were you when Trotsky took his Red Army against the hapless party dissidents of the Baltic fleet, and mowed them down?

For Kronstadt, read Trident. Jeremy Corbyn’s commissars are hunting down the moderates, demanding to see the peasant dirt under their fingernails and asking where they stand on CND. Are they with the Great Leader, or are they with the rightwing pigs of the nuclear arms lobby? Nice people, these.

I am mystified. How did Hilary Benn, Maria Eagle, Charles Falconer and Paul Kenny, among others, come to choose the Trident nuclear missile as the totem of revolt against the Corbynites? Amid all the rubbish the Labour left espoused, defence has stood out as a beacon of sanity.

Corbyn was right on Iraq. He was right on Syria. He is right on Islamic State. On the idiocy, waste and vacuous drivel that constitutes “the case for Trident”, he has been right. Fighting him on it just to make Labour seem macho makes no sense.

Defence is an area where governments are notoriously beholden to archaism and special interests – and where oppositions have a duty of challenge. The idea that opposition to the renewal of Trident is an extreme policy confined to the British left is absurd. Anyone reading the recent literature on the nuclear deterrent can reach only one conclusion. It is daft.

How did Hilary Benn, Maria Eagle, Charles Falconer and Paul Kenny choose Trident as the totem of revolt?

When the late defence chief Michael Carver famously asked of Trident, “What the bloody hell is it for?”, an informed guess was that roughly half his senior colleagues agreed, including most army generals. Former defence secretaries Des Browne (Labour) and Michael Portillo (Conservative) have come out against Trident. So have military experts from Hugh Beach to Patrick Cordingley. So has the formerly pro-nuclear defence pundit Michael Howard.

Trident’s defenders have been largely confined to naval and defence industry lobbyists and a few Conservative MPs. The late Michael Quinlan, for long the high priest of nuclear deterrence, scrupulously held that the case needed regular review. In his final Chatham House essay (and then book) in 2006, he doubted if the “highly unspecific strategic arguments” for a separate British deterrent would long justify its soaring cost.

Since the coalition government came to power in 2010, immunity to reason has been obligatory among Trident apologists. Rumour had it that Cameron, possibly on Trident and certainly on aircraft carriers, was a sceptic. That was before the lobbies got to him. The cost of the programme soared from £20bn in 2004 to somewhere north of £100bn today and fails to stop. Quinlan would surely have washed his hands at this point. The new Astute class submarines, replacing Vanguard, have been cursed by cost and technical problems.

At the end of last year George Osborne took such fright at Trident’s chaotic cost as to remove the programme entirely from defence control and bring it under the Treasury. With grim humour, he equated it to the Olympics and HS2, thus stamping it as reckless vanity with no known link to sanity.

Trident seems to bring out the worst in politicians. Cameron recently said that Trident was needed to defend Britain against North Korea. Did he really get a first class degree in politics, philosophy and economics? Others have cited Trident variously against Isis, random terrorists, and a resurgent Russia. It is on a par with Sir Humphrey in Yes, Prime Minister, who said it was to deter France.

The cast of the new Dad’s Army film. ‘We can imagine swarms of terrorists charging ashore off the Dover ferry, but it would make more sense putting Dad’s Army back in uniform and issuing teachers with machine guns.’ Photograph: Universal Pictures/PA

All declared threats to Britain tend to come either from powers with no conceivable designs on conquering Britain or from forces immune to deterrence. Nor has anyone explained why, if Trident is so vital to Britain’s safety, that is not true for the 25 non-nuclear Nato states, not to mention almost all other countries in the world.

Even the more articulate defenders of Trident, such as the Tory MP Julian Lewis, must fall back on unspecific ideals of world influence and “insurance”, without ever defining a deter-able threat. Britain’s bomb cut no ice with Leopoldo Galtieri, Slobodan Milošević or Saddam Hussein. We can imagine swarms of terrorists charging ashore off the Dover ferry, but it would make more sense putting Dad’s Army back in uniform and issuing teachers with machine guns.

Today Trident’s chief enemy is neither Corbyn nor the Treasury. It is technology. Renewal is besieged by questions about cyber security.

More severe is whether these giant manned weapons have any future anyway. It is stupid enough spending billions on carriers when bombing wars are increasingly conducted by drones. It now appears that submarines will be vulnerable to squadrons of underwater drones, armed and able to read their every move. A seaborne missile may be as obsolete as a medieval warhorse in the age of the rifle.

Historians such as Richard Rhodes and Andrew Alexander have catalogued the Nato mendacity and fear-mongering that was the cold war arms race with Russia. Rhodes’s Arsenals of Folly showed such recklessness raised rather than lowered the risk of nuclear miscalculation. The blatant use of fear by Cameron and others today is no less disingenuous. Any thinking person must know that the only defence against any sensible risk to British security today is a well-equipped ground force. Implausible and unusable weapons are pure waste.

When, back in 2007, Tony Blair was first pondering the renewal of Trident, he wrote in his memoir that he found the case dubious – and Gordon Brown agreed. Switching the money to something else “would not have been stupid”. But he then tried to imagine getting up in parliament to say he was giving up the British bomb, and merely thought, “We’re not going to say it, are we?” In other words, why bother with the right thing, when you can go on buying toys with other people’s money?

Given the history of nuclear scepticism within Labour, where Trident was long seen as a virility symbol of soundness on defence, it is bizarre of Corbyn’s foes to use this, of all policies, as a stick with which to beat him. For once he is right. Support him.