Something pure and beautiful was defaced by mindless cretins.

On a glorious afternoon of top-class soccer, Manchester City and Manchester United went head-to-head for first place -- and perhaps the championship -- in the Barclays Premier League . The game ebbed and flowed, with City washing over United's half early, yet going down two against the run of play, then receding somewhat but somehow equalizing. But in injury time, Robin van Persie twirled in a free kick, which took a friendly deflection, for United's game-winner. An instant classic. A testy but speedy and skillfully executed contest that held two comebacks and a last-gasp winner. All that is good about the sport: the very best at their very best.

And then it changed.

United defender Rio Ferdinand ran over to the visiting fans to celebrate with his peers, only to be struck above the eyebrow with a coin tossed by a City fan. Racial abuse allegedly cascaded over him from the stands , sending police into the fray. A fan ran onto the field to accost Ferdinand some more but was intercepted by City goalkeeper Joe Hart.

One of the most exciting games of the last year was ruined. The lines surrounding the field blurred and then crossed by the outside world. The big glossy bubble burst by a quick jab from a tiny needle.

The beauty of sport is its humanity. But its attraction lies in its capacity for escapism too. What happens in it ultimately doesn't matter in the grand scheme of things. It's just entertainment; only a game. All that happens is so blissfully inconsequential. Yet we can attach however much importance to it as we choose -- invest or divest.

We live vicariously. We vent and we cheer. We sulk and we celebrate. We briefly revel in the outer boundaries of our emotions in a way we wouldn't like to in our private lives, where action and reaction matter. That's the point. Sport is a conduit. A proxy. It's a safe place, where no amount of good luck or misfortune can taint your daily life. Separation of church and state.

But when the escapism passes into reality, it no longer serves the outlet. To burden it with your intrusion is to taint it and, ultimately, to destroy it. The fun is to think your cheering or cursing has influence when really it doesn't. But when your actions do interfere, the mirage vanishes and it becomes just another troubled reality. That's what happened in Manchester on Sunday. A marvelous spectacle, the likes of which are rare and the observers of which are privileged, was ruined for many by just a few.

So much ugliness didn't occur in a vacuum. Soccer violence is on the rise in several European countries, places where it had been all but exterminated for a decade or more. With an economy that has turned bad and only promises to get worse, entire societies are on edge. Citizens are being asked to turn in the spoils and perks accrued over a generation. Today's workforce will have it worse than the one that preceded it. It's unnatural; counter-evolutionary.

Resentment inevitably seethes. A rage swells within the populace hardest hit. And it can send them over the brink unthinkingly by a seemingly innocuous instigation. Like a last-gasp winner by the crosstown rivals.

The events in Manchester were inexcusable. Yet somehow understandable. Not that we would do the same or somehow condone the acts of the accused. But in that we can trace the anger to its origins and share an empathy over its symptoms.

The point of sports is that we can release some of that anger. Sometimes it is even productive. Like the countless times the shared yoke suffered by soccer fans galvanized them to become agents of change -- most recently when Egyptians set their minds to overthrowing a longtime despot.

This is not one of those times.

This time, all that was accomplished was that perhaps the greatest game yet in a burgeoning rivalry, between one side of the city against the other, between the old money and the nouveaux riches, was relegated to an incident.

And that's the real tragedy.