Now we have seen enough horror and atrocity to recognise what comes after: the bewilderment, the shock and anguish – and then, in the cold light of day, the attempt to make sense of the senseless by way of context and community leadership.

By this morning, Manchester’s leaders and community figures were seeking to react, grasping for the right pitch and tone. Andy Burnham, the newly elected mayor of Greater Manchester, spoke well – as did local commentator Mohammed Shafiq, mindful of the need for a Muslim voice to be heard in condemnation.

But on these occasions, location is usually incidental. They meet the very definition of terrorism: acts of brutality leveraged to achieve a much larger degree of national hurt and international anxiety. They call upon national leaders to display the requisite degree of national leadership. But we have yet to see that.

We have seen what we always see. The home secretary, Amber Rudd, rightly praised “the great city of Manchester”, and condemned the atrocity. “Its intention was to sow fear – its intention is to divide. But it will not succeed,” she said. The prime minister also spoke outside Downing Street of the “appalling, sickening cowardice” of the attackers, the spirit of Manchester, and the spirit of Britain, which had never been broken despite “years of conflict and terrorism”.

Both sought to be robust, and yet both fell short. Because we know that after the shock and the anger – in the face of pleas for unity – comes the search for scapegoats, which makes that unity so much harder to achieve.

Even if Hopkins knows nothing of Nazism - which I doubt - her "final solution" can only mean ethnic cleansing pic.twitter.com/U7SDYh4e8q — Nick Cohen (@NickCohen4) May 23, 2017

Before the cries had died down, or any facts come to light, with the injured still being treated and with desperate families still looking for their loved ones, the ghoulish process was begun, by the columnist and broadcaster Katie Hopkins: a figure who masquerades as a journalist but whose commercial USP is the public peddling of indecency to her own pecuniary advantage.

“Do not be part of the problem,” read her tweet, aimed at TV presenter Philip Schofield, part of an inflammatory series in the aftermath of the attack. “We need a final solution. #Machester [sic].”

Facing immediate condemnation, she modified the intervention, exchanging “final solution”, with its associations to the Holocaust, to “true solution”. But by then the object had been achieved; Hopkins had, by pushing the envelope as far as she could, without care for the consequences, inserted herself into the debate.

Free speech, even if it’s recklessly divisive, is a prerequisite in a free society. Illustration: Ellie Foreman-Peck

Ignore Hopkins, many say. Sometimes that seems the wisest course – for free speech, even recklessly divisive free speech, is a prerequisite in a free society. But some speech is so inflammatory and societally divisive that we enact laws to prevent it.

Public exhortations for an apparent “final solution” and urging “western men” to protect their families seem to fall into that category. Critics have reported Hopkins to the police, calling on them to investigate her for a possible criminal offence. Officers should do so.

For, again, we know what happens next. It starts with the likes of Hopkins saying what should be legally and decently unsayable, and further down the same rutted path we encounter the Telegraph columnist Allison Pearson with her own tweeted observation that “we need internment of thousands of terror suspects now to protect our children”.

We need a State of Emergency as France has. We need internment of thousands of terror suspects now to protect our children. #Manchester — Allison Pearson (@allisonpearson) May 23, 2017

And we know what happens after that, when those who hold the megaphone use it to drive anger to higher heights and to inflame tensions. We saw it after the highly toxic referendum campaign, when the number of hate crimes leapt by 41%, according to the Home Office. It begins with those who abuse their licence in a free society to make deliberately incendiary comments; it ends in fractured, fearful communities and cracked heads.

It is the job of the home secretary, the prime minister and the police to protect those societies. If our communities are largely harmonious, that is in part because people of goodwill, of many colours, of many origins, strive to make them so. But it is also because the rule of law provides a framework. It is absolutely the job of the prime minister and the home secretary to speak of the kindness and public spiritedness that manifests itself in terrible times such as this – and both did so well – but it is also their job to make it clear that the unity we hold dear stems from the rule of law.

There is a leadership that says we will all pull together, because we always do. But just once I’d like to see that allied to leadership that also says: we understand this is a time of great tension; we know that there are opportunities for those of malign intent to exacerbate those tensions – for political gain, for notoriety, or financial enrichment; and we need them to be aware that the wider society we represent will not tolerate it.

Such leadership says this is not open season. There will be no intellectual equivalent of looting amid the devastation. Society will protect the vulnerable. The rule of law will apply. Those who breach it in word or deed render themselves liable to prosecution.

There is all-pervasive incivility in this angry age of illiberalism and social media – that, as democrats, we have to stomach. There are those who would attack us with bombs and knives. We expect nothing from them but nihilism and brutality. But a society undermined from within at a time of crisis needs champions unequivocally prepared to protect it. We elect and employ such people. It is their job, and they should leave no doubt that they will do it.