Gary Neville was right. It might have struck a jarring note in the post-match Sky Sports studio, sandwiched between the unsmiling platitudes of Roy Keane and an ad-break sting. But Neville was right to state that for the last few years British politicians have deliberately, or at best carelessly [narrator: it was deliberate], leveraged racial tensions for political gain.

Don’t just take Gary’s word for it. Ask the UN, who have in the last year criticised British politics for exactly this, with specific reference to the “hostile environment” shambles on immigration policy and the insidious rhetoric around Brexit. These things don’t happen in a vacuum. There is a price to be paid.

On Monday it emerged Tottenham Hotspur had expelled a child from their stadium for allegedly racially abusing Son Heung-min during the game against Burnley. Elsewhere two Wolves supporters were ejected from the Amex Stadium for homophobic abuse, another form of viciousness on the rise at football, as it is elsewhere.

So Neville was right to talk about politics in response to the news a man in the crowd had appeared to racially abuse Manchester United players at the Etihad on Saturday. Firstly because if not now, then when? And secondly because politics is talking to sport all the time, informing its tone, its voice, its discourse.

Neville was right also to refer specifically to Boris Johnson, who has ridden these tides more successfully than anyone else. When Johnson pronounces on immigration or presents himself as the hammer of the shadowy ruling elites, it is still hard to feel he really believes what he’s saying himself, hard to conclude he isn’t simply doing this to score points, or simply because he knows it works. This is where we’re at now: a prime minister so inauthentic you start to suspect he isn’t even a real racist.

Credit where it’s due, though. In his tribalism and his command of division Johnson appears to have a perfect understanding of the way crowds work. And beyond that, of the way the shouty polarities of public life have begun to follow a familiar football-crowd pattern: to be so easily led, and so easily led the wrong way.

With this in mind it was heartening to hear that Pep Guardiola had comforted Fred in the tunnel after the Manchester derby, although Fred says he wasn’t aware of the abuse until he returned to the dressing room and saw the TV footage (for the record, the man in question insists he is innocent and was simply putting his hands down his pants).

It was also encouraging to hear Ole Gunnar Solskjær try to separate the two elements – racist abuse, club identity – in his post-match press conference. It was entirely right, too, that City have promised to take immediate and decisive action. This is not a problem the club has historically carried. City are from Moss Side originally, a racially mixed part of Manchester. Black supporters and players have long been a part of the club, from locals such as Alex Williams to the more recent roster of stars.

This is the good side of Saturday afternoon. As for the bad side, well, that starts pretty much everywhere else and goes on from there. East Manchester was a poisonous place generally, not helped by the witless decision to kick off at 5.30pm. The vibe at the Etihad was fractious, pent-up and – let’s face it – jaw-grindingly intoxicated in parts.

Zoom out a little wider and from the moment pictures of the alleged abuse first appeared on the internet the digital periphery was jammed with the usual tide of blame, finger-jabbing and that particularly modern strain of gloating that seems to have little to do with rectifying the ills of prejudice and division.

It is by now a familiar cycle, what we might call the Evra Dialectic. A racist incident happens. Outrage follows, much of it oddly gleeful, characterised by name-calling and demonising of other fans of the “guilty” club.

A vocal subsection will then reply by “backing their man”: dissembling, denying, blaming “the media”, listing the other club’s own assorted wrongs. And so we enter the dead zone of insults and counter-claim, deluded badge-loyalties and a refusal to accept the evidence of our own eyes.

It is a trap football falls into so easily and at every level. Perhaps it is time to talk again about Guardiola, who a year ago blamed the media, with some justification, for publishing racist stereotypes that contributed to the abuse of Raheem Sterling at Chelsea.

Fast-forward to Bernardo Silva, Twitter and the publication of a more guileless form of cartoon stereotype on the internet, for which Silva received a one-match ban from the FA. This time Guardiola backed his man to the hilt, refused to offer any condemnation, defending pretty much the same kind of ill he had so righteously condemned.

Three months later we have monkey chants at the Etihad. The two are not directly connected, of course. Idiots need little assistance to be idiots. But as has been quite rightly levelled at the wretched Johnson, leaders also have a responsibility to set a tone, to show the best of us. One lesson of our current politics is that people listen to the messages they’re given.

Blind tribalism is also something football can resist. So much hard work is poured into education and regulation by well-meaning but essentially limited organisations such as Kick It Out. So much glossy lip service is offered by the sport’s authorities. But those who watch and support have an agency of their own, the ability to act as a balm not an irritant.

Perhaps it might be wise to start by changing fundamentally the way football talks about these incidents, by moving away from the idea that this is “a Manchester City fan” who stands accused of abusing Fred. Club loyalties are irrelevant here, as they are in every other form of crime.

Everyone loses, everyone suffers in this situation, just as everyone should feel sympathy and regret, not simply those who wear the same replica shirt.

Backing your man, backing your tribe, dealing only in blame and division – this is the poison football, sport, everybody with a vote needs to resist.