Has there ever been a stranger political occasion than Tuesday night’s marathon meeting of Labour’s national executive committee? In an abridged version, the events of those six hours may one day make a good play, awash not just with division and bitterness, but plenty of bathos – from the moment when “the office took a delivery of four crates of sandwiches”, to the aftermath when, in tribute to her leader’s solidarity with the downtrodden, a jubilant member of Jeremy Corbyn’s Westminster team tweeted a picture of two bottles of House of Commons champagne, with the simple caption, “Sweet”. Inside an hour, she had deleted it. Funny, that.

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Three decisions taken that night speak volumes about the party’s grim predicament. Whatever the whys and wherefores of that botched “coup”, there is something undeniably odd about a party leader who would apparently struggle to get the support of 51 MPs and MEPs, and the need for a vote to let him on the ballot paper regardless. Stranger still are the new rules on who exactly can vote (which rule out people who have joined in the last six months, while apparently leaving open the possibility than they can resign their memberships, re-register as “supporters”, and then pay £25 to participate). Finally, perhaps the most striking decision of all: the imposition of a kind of internal martial law, whereby “all normal party meetings at CLP and branch level shall be suspended until the completion of the leadership election”.

This is drastic stuff – the party effectively putting its daily operations into suspended animation - and the explanation is obvious enough. There is a fetid cloud of acrimony and spite hanging over Labour, and no end of reports of hateful behaviour dating back to long before this crisis; some of it clearly the preserve of lone inadequates, but other aspects reflective of the old political calculation whereby adversaries are best beaten by making their lives so unpleasant that they simply give up.

Rosie Winterton, the Labour chief whip, has made formal representations to prominent Corbyn allies about the abuse and harassment of MPs. We all know about the brick put through the window of Angela Eagle’s constituency office. Eagle has also had to cancel a forthcoming meeting in Luton after “threatening” phone calls. According to a party member who said she felt “threatened” and ended up in tears, a meeting of the Bristol West constituency party last Thursday saw a hardcore of Corbyn supporters “shouting and screaming” not just at the local MP who had resigned her shadow ministerial post, but “the chair, and anyone with an opposing view, as if they were shouting at Cameron on a protest march”.

In Brighton, the pro-Corbyn group Momentum organised a rally just prior to the local Labour party’s annual meeting last Saturday. There was then a massed walk from one to other, where serving party officers were all summarily replaced by Corbynites. The edges of the meeting were reportedly characterised by what one insider described as “a real nastiness”, manifested in the caretaker of the building being spat at, while two Corbyn supporters later claimed to have been called “scum” and threatened with violence.

Social media is full of the hateful discourse in which criticism is tantamount to treachery

Meanwhile, confirming that social media is probably the worst thing that ever happened to the political left, it is full of the hateful discourse in which criticism is tantamount to treachery, and misogyny and antisemitism are never far away. The people responsible are apparently unconcerned about the fact that grinding the Labour party into dust on platforms provided by mega-earning capitalists suggests a certain kind of abject collaboration, but there we are.

Clearly, there are elements from all wings of the party prone to horrible behaviour. But let’s not mess about: right now, the lion’s share of the noise is coming from people who evidently see what they’re doing as part of the defence of their embattled leader. Whether particular elements of the party – Momentum, chiefly – have authorised any of this is hardly the point: of course they haven’t, and many of their people are appalled. But there is also a sense that awful stuff is being tacitly tolerated, as the seriousness of what is happening is either underestimated or completely ignored.

Facebook Twitter Pinterest John McDonnell. This is a politics that ‘is far too macho, privileging the kind of gobby men who accuse their colleagues of being ‘fucking useless’’. Photograph: Daniel Leal-Olivas/PA

If you doubt this, listen to the Radio 4 interview given by Johanna Baxter, an NEC member from Scotland, describing the meeting and the atmosphere surrounding it. She sounded nervous and close to tears, and with good reason: if you’d had your mobile phone number posted online, and if women colleagues had described rape and death threats, you would be too. For these reasons she urged that the decision on Corbyn be put to a secret ballot – a proposal the leader opposed. “I acknowledge Jeremy has consistently spoken against bullying behaviour and I applaud him for that,” she said. “But when it came to the vote to prevent colleagues taking an extremely difficult decision that would determine the future of our party, he voted against the single thing that he could have done to protect those colleagues.”

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Underneath all this, it pains me to say, is a politics that lays claim to high humanitarian ideals, while either practising or tolerating the opposite. It is far too macho, privileging the kind of gobby men who accuse their colleagues of being “fucking useless”, and worse, and neglecting the ways in which less privileged voices might be brought into the conversation. It also represents the outer edge of one of the strands of support for Corbyn that may yet prove to be its downfall: the politics of puritanism, whereby no compromise can ever be brooked, and to even question the leader’s bona fides is to ally oneself with “Blairites”, “warmongers”, and worse.

Just to be clear: the Labour party’s collective ethics have hardly taken this terrible turn after a long spell of loveliness. Down the years, most elements of the left have fallen for the idea that so long as the ends embody this or that lofty principle, the means can be as unpleasant as need be. In that sense, driving people away from meetings and traducing them on Twitter is surely on the same moral spectrum as things that happened in the Blair and Brown years: the fixing of selections, pressuring conference delegates into reading out pre-written speeches, the attempted destruction of people’s careers via “briefing”.

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So, though it hardly excuses any of the awfulness, the party is perhaps reaping its own whirlwind: when an organisation’s moral centre implodes (and here, it’s worth the obligatory mention of Iraq), anything goes.

All of which adds to the reek of death, and the sense that this collapse into acrimony is of a piece with Labour’s estrangement from its traditional working-class base, the increasing dominance of a metropolitan hardcore, and the clear impression of unstoppable decline. Corbyn might be bereft of responses to all this, but neither Eagle nor Owen Smith have so far come up with any convincing answers, beyond either the former’s appeal to a hackneyed Labour identity which no longer chimes with the real world (“I’m a strong Labour woman”), or the latter’s reheated version of tax-and-spend social democracy.

At this rate one or both of them will lose, and God only knows what Labour will turn into: a dystopia of intolerance, in all likelihood, from which anyone with any self-respect will walk away.

• The headline on this article was amended on 15 July 2016 to avoid unintended offence