If it doesn't seem odd, it's because you weren't there. When Atlético Madrid played Liverpool in the Champions League on Wednesday, the referee was given specific instructions to halt the match at once if there was any monkey-chanting or throwing of bananas.

There was a time, not a quarter-century back, when no football match could start without a volley of bananas and a chorus of welcoming ooh-ooh-oohs at the opposition's lone black player - who was always, of course, on the left wing.

It is a quite remarkable change. Racism was accepted. Deplored by some, propagated by many, it was an apparently ineradicable part of football. From the first division, as the first division in football was then called, sliding down the pyramid into the non-league game, every black player was fair game. Monkey! Ooh-ooh-ooh!

The very thought seems absurd these days, as impossible as terraces, rattles, footballers running a pub when they retired, the local builder as chairman, National Service, Armand and Michaela Denis, Hans and Lotte Hass, Pathé News and, well, The Black and White Minstrel Show.

Not that the ancient tradition of abuse has ended. That's more virulent than ever before: Manchester United can be taunted about the Munich air disaster, Arsène Wenger can be called a paedophile, Graeme Le Saux was invariably told he was a poof and a queer. There seems no end to it, but there is. You can call anyone in football a bastard - but as soon as you call him a black bastard, you have stepped over the line.

Any hint of racism is totally unacceptable, and if the people around you don't tell you to shut up, the stewards will, and they'll probably eject you as well. You can heap all kinds of vile abuse on anyone you like - particularly if you have sought safety in numbers and are singing along to an abusive song - but once you step over the racist line, you can expect no mercy.

It is the ultimate crime, the sin for which there is no forgiveness. And it represents the most extraordinary shift in perception. Abuse continues, and it can be utterly shocking. Steve McClaren was abused so strongly at England's disappointing - though still victorious - display against Andorra in Barcelona last year that all sane people instantly hoped that he would lead England to the World Cup at the very least.

This season, Sol Campbell, playing for Portsmouth, was subjected to homophobic abuse, and if you have the stomach, and you can find it on YouTube, it's something the abusers are clearly proud of. Ashley Cole was booed and abused after a mistake playing for England. Both these players are black. Their colour may have inspired the abuse but their colour was not its subject - and that, apparently, makes it all right.

Open racist abuse is deplored by one and all. It's a triumph, yes, a revolution in thinking, but the situation is not one of simple self-congratulation - for all that we get frightfully snooty these days about outbreaks of racism among Spaniards and Croats, as if English football has a long and impressive record of civilised behaviour and has the right to lecture the world on the subject.

It's worth raising a cap to the campaigners, to all those involved in Let's Kick Racism Out of Football and so forth. We should also recognise that these days, just about all teams have players of all shades of skin. Abuse a race and you abuse your own side; and self-abuse is best avoided, at least in public.

But the most important factor in the decline of racism in football is great black footballers. Football has given us an unending series of inspirational players and many of them have not been entirely pinko-grey of countenance. Campaigners do what they can, but people such as John Barnes, Ruud Gullit and Paul Ince do a lot more.

Some might say that football is just reflecting changes in society, but I think football has been an active force for change. Football has helped to lead society away from its instinctive racism. It has provided black heroes. Barnes's goal against Brazil at the Maracanã in 1984 - that's on YouTube as well if you haven't seen it - gave joy to the nation; who could fail to cheer at its beauty? It seemed that Barnes was working a pincer-movement on our basic instincts, in partnership with Naomi Campbell.

It's undeniable: football has been a beacon of progressive thought and sanity. That is not to say that racism has been eradicated in this country, but at a time when football brings us black heroes on a daily basis, we at least have different views of what racism means. We have different targets: Asians, especially Muslims, asylum-seekers, East European migrant workers. Let's not get smug. And there is a sense in which football's curiously total victory over racism is a compromised triumph.

It is as if the prohibition on racism means that everything else is permitted. If we are to deny ourselves the pleasures of racist abuse, it is only fair to allow ourselves every other form of abuse - while considering ourselves saints for our restraint.

You are of illegitimate birth, you are homosexual, you are an onanist, your wife indulges in eccentric and promiscuous sexual practices, your own tastes are severely compromised, you're a traitor, you are Judas, you are obsessed with money, you are incompetent, you sexually abuse children, you're black - What! Hang on a minute, you can't say that! That's absolutely dreadful! What sort of people do you think we are? We don't tolerate that sort of thing round here, thank you very much. Now be quiet, I think the boys at the back are going to sing the paedophile song again in a minute.

Racism is bad, but its apparent conquest gives football (and perhaps society beyond football) the altogether inappropriate belief that every ill has been overcome. By concentrating on the single evil of racism, many other evils are accepted.

But what is so fascinating here is that even this can be changed. If we can have football without bananas, it is possible to have football without other forms of abuse, other kinds of vileness. I do not concede that vileness is “part of football”. Rivalry is, hatred is not.

It would once have been considered hopelessly idealistic, head-in-the-clouds stuff put about by people altogether out of touch with gritty reality, to suggest that black players would one day be accepted in football without insult, without bananas. But that has changed utterly, thanks to campaign, example, enforcement and above all, a genuine will for change. The point is not to stop there. Greater decency, less hatred; such things are within the grasp of us all, for they are aspects of being human.

Let us look, then, for expanding circles of intolerance. Racist abuse is no longer tolerated at football matches in this country; good. But what is the next circle of intolerance that football can encompass? Is it homophobia? Accusations of sexual idiosyncrasy? Vindictive abuse of individuals? Who is to say? All I know is that football will be a better game, and ours will be a better society, when we expand into the next circle of intolerance.