From the outset of Jeremy Corbyn’s rise to the leadership, a narrative has haunted him: that his politics are stuck in the past, and that, despite all his personal decency, he and his allies are irrational – obsessed with a lost moral crusade, trying to settle decades-old scores inside the Labour Party. If the past few weeks have shown anything, it is that it is actually Corbyn’s opponents inside the Labour Party who exhibit these traits the most.

During the period running up to the vote on Syrian intervention, Momentum organised a campaign of letter-writing and lobbying of Labour MPs. There were many polite emails, some angry ones, and some outright abuse. Since then, there has been a newfound level of bile directed at the fledgling network of Corbyn supporters: a member of Corbyn’s Shadow Cabinet went on record to say that their “aggression is matched only by their stupidity”, while other MPs demanded that Corbyn “disband” the whole enterprise.

Most telling has been the reaction of MPs to the idea of deselection and mandatory reselection. Many of them discuss it in the same terms that they would discuss a coming nuclear war. Others attack the idea as “mob rule”. The out of proportion and knee-jerk reaction directed at the idea of reselection, lobbying MPs and Momentum is rooted in all kinds of historical baggage – and it is the exact opposite of the sensible, moderate politics that Corbyn’s opponents claim to embody. To much of the public, it makes no sense: having accountable representatives may well look like a good thing. And coming from MPs and leading figures on the right of the party, who are clearly factionally organised themselves, it is transparently hypocritical.

On the one hand, there is no doubt that all the talk of bullying and the hyperbole about deselection presents a major problem for Corbyn’s leadership. At a time when absorbing and mobilising new members is more important than at any other point in its history, much of Labour – on the left and the right of the party – is being forced to cope with a constant stream of collisions between a new mass politics and the PLP, some of whom can no longer contain their disdain for it. On the other hand, Labour is getting what it needs: an exorcism, in which all of the Party’s demons are being drawn out.

The ‘modernisation’ of the Labour Party undertaken by Neil Kinnock and Tony Blair was not about shifting the base of Labour’s supporters directly: it was fundamentally an attempt to wall off the parliamentary party from the wider labour movement via a series of constitutional amendments and symbolic policy shifts, at a time when the wider movement was in retreat from a series of gruelling industrial and political defeats. Jeremy Corbyn’s great act of modernisation – perhaps the only alternative to a perpetual cycle of rightward drift – will be to reconnect the party to a new layer of social movements and organised workers.

The forces that this process will unleash inside the Labour Party – in every ward, CLP and internal election – are overwhelming, and some centrists in the party are panicking. They are invoking the 1980s, they are briefing the press constantly and self-destructively, they are insisting that mass participation constitutes bullying in itself. Most of the public neither understands nor cares about much of this rancour, informed as it is by decades-old historical baggage, beyond the impression of internal chaos that it radiates.

For those on the right of the party who understand what they’re doing, the constant stream of disquiet about the grave threat that the left poses is not designed to win back a majority of the party membership in short order – because that battle is already lost. Labour’s membership has grown exponentially, and among the membership it looks like there is now a higher approval rating for Corbyn than there was in September when he was elected. What many on the right of the PLP are now engaged in is a kind of asymmetrical warfare – an attempt to force errors on the part of the Corbyn leadership.

The first thing the left must do in response is to maintain focus. Much like the Conservative press machine, much of the internal dissent has had the effect of focussing the national debate onto security and foreign policy – and away from social and economic policy, where Corbyn enjoys high levels of support well beyond party lines. Syria, like Trident, is important, but if it dominates too much, both Corbyn and the wider left will look out of touch.

The second thing is to hold its nerve and not to allow dissent from the right to unleash divisions within the left. The left has demons of its own, and they are beginning to show up at Momentum meetings – not so much in the proliferation of Trotskyist newspapers, but in the reaction of some Labour left organisers to their presence. If the presence of political literature is seen as a liability, or Momentum fails to organise inside Labour for fear of upsetting the press, then to an extent the right has already won.

While Labour’s right wing kicks and screams, and briefs every corner of the press, the activist left within the party must simply go about their business calmly and respectfully, reach out face-to-face to the wider public, and wait for the exorcism to pass.