The footage, taken at Richelieu-Drouot station on the Paris Metro on Tuesday evening, lasts just 57 seconds. And, some say, it takes us back 40 years. You will quite possibly have watched it: white, out-of-shape, so-called Chelsea supporters twice blocking a black man as he tries to board their train as they travelled to the Champions League tie against Paris St Germain.
They twice push him off. A black woman standing beside their carriage backs away as they sing: "We're racist. We're racist. That's the way we like it." This is revolting stuff: cowardly, horrible, and, let's not forget, criminal. It shows the travelling "fan" at his worst; drunk, racist, and secure only in the like-minded company of other pathetic souls.
John Murray, the BBC football reporter, was first out of the blocks when he said on Radio 4's Today programme that the incident seemed to mark a return to the 1970s. Others agreed. It was an understandable reaction. But really?
Many of us recall the days of Steaming In, Colin Ward's fascinating account of life on the football terraces back in the 1970s and '80s. Hooliganism was a way of life: matches were military operations; both for rival sets of fans intent on battering seven bells out of each other and for the unlucky police forces trying to prevent them. And racism was endemic.
In the mid-1980s, a few friends and I often met in the pub on a Saturday lunchtime. We would decide which top-level game we fancied and then we'd toddle along and pay at the gate.
You could do that in those pre-gentrification days and we sometimes went to Stamford Bridge. Chelsea then had a young left-back called Keith Dublin. And the fans - a sizeable proportion of them, anyway - detested him. Why? Because he was black.
On my first visit, he was booed throughout - awful stuff: monkey noises, the most violent spit-flecked abuse imaginable - and his confidence, not surprisingly, was shot. I finally turned on the worst abuser; there was a half-hearted, windmilling fracas; and a rather nervous truce afterwards. Needless to say, the police and stewards didn't get involved. Nor, significantly, did it even occur to me to alert them.
So, no, we are not back there. And, in many ways, the immediate reaction to the footage is heartening. Chelsea acted swiftly and clearly; there is little doubt that these disgusting individuals will be traced and banned for life. The chances are, I would bet, they will be jailed, too. Good riddance.
The bravery of their target was rather uplifting. He appears bemused, but self-confident, and the contempt of the woman who backs away is withering. Bystander Paul Nolan's mobile phone footage was quickly online and has gone viral. Right-thinking anger has similarly mushroomed. Such racism is indeed less overt than it was. Society has moved on and football, for a whole host of reasons, has, too. But scratch the surface, and it's sometimes not so far away.
The supporters probably wouldn't feel the need to indulge in such racist behaviour in London these days, even if some of them might think it.
And what are we to make of the fact that six of the 18 players Chelsea named on Tuesday night were black?
Would any of the people captured on Mr Nolan's film be unhappy if one of Chelsea's black players had scored? Of course not, but possibly only on the "he-may-be-black-but-he's-one-of-ours-so-that's-okay" principle.
Supporters do like an Us vs The World scenario. Take Glasgow. Rangers are traditionally Protestant while Celtic's roots are in the Catholic Irish immigrant community. Back in the 1970s, sectarianism was expressed in violent mayhem. Terrace chants had little to do with football and there were arrests at every match.
There were improvements after Rangers, under manager Graeme Souness, signed their first Catholic, Mo Johnston, in 1989. Fans who still believed in the idea of Orange supremacy soon found themselves cheering on a side containing a majority of Catholics.
And into this situation, one return to the 1970s is being contemplated north of the border. After one vicious clash too many - the Scottish Cup final of 1980, where Rangers and Celtic fans fought on the pitch at the final whistle - alcohol was banned at football matches. Jim Murphy, the new leader of Scottish Labour, and a teetotaller, incidentally, is suggesting it is time to overturn this policy. His argument? Rugby fans can do it; English football fans can do it. Why not the working man?
Lastly, on the footage from Paris. It does feel like the last stand of the losers. Maybe that's the biggest change of all.