Normally, when we think of the victims of unprovoked violent crime, the images that come to mind are of old people living alone or of vulnerable women on the street at night.

If fit young men between the ages of 14 and 23 enter the picture, it is as perpetrators, not as victims. Yet, if you talk at all to parents of young men in those age groups, the chances are that the stories of casual, sometimes repeated, assaults emerge.

Although the official crime statistics are not detailed enough to isolate this category of violence, few people doubt that, in every urban area, attacks on men in their teenage and young adult years have become almost a fact of life. This week's figures from Victim Support tend to bear out this perception.

Like all crime scares, this one needs to be treated with a degree of caution. It is worth bearing in mind that Irish towns and cities are generally safer than most of their European equivalents. Horror stories, moreover, lend themselves to exaggeration. The attack on a 12-year-old German girl which provoked justified outrage this week was certainly bad. But the most lurid detail in the initial reports - that the victim had been slashed across the face with a broken bottle - turned out to be almost certainly untrue.

Scepticism goes only so far. In relation to attacks on young men, indeed, it may well be that the reality has been more often underplayed than hyped. Rightly or wrongly, many victims tend to believe that their suffering will be taken less seriously than attacks on more obviously vulnerable people.

There is still a general assumption that a big young fellow should be able to take care of himself, and that, if he gets a few digs, it's at least partly his own fault. For all the supposed revolution in attitudes to gender, macho stereotypes haven't gone away and, if anything, have been hugely reinforced by laddish popular culture. Since real men can look after themselves, those who get beaten up are made to feel ashamed of their own supposed weakness.

SO what's going on? There is no shortage of off-the-shelf explanations, but none of them is very convincing. The currently fashionable notion that men have become redundant might be a lot more persuasive if there were not also strong evidence of a rise in violent assaults perpetrated by young women. Quite often the gangs who carry out street attacks have a number of girls in them, and not simply as passive observers.

One of the most popular explanations - that it's all down to violence on television and in the movies - is superficially persuasive, not least because it has more than a grain of truth. There is a new kind of glorification of yobs and bullies in popular entertainment. Films targeted at young men - think of Pulp Fiction or Lock, Stock and Two Smoking Barrels - are characterised by a new kind of chic thuggery and an utterly unapologetic contempt for the victims of violence. That cultural climate can't be entirely irrelevant.

But neither is it anything like a persuasive explanation. If television and the movies are the cause of aggression on the streets, how come, in the 18th century, no sane gentleman would have ventured on to the streets of any major city after dark without a sword?

The frequency of unprovoked assaults on young men may have increased, but no one can seriously believe that the phenomenon is a new one. What's changed, in fact, is not the crime itself, but the nature of the society in which it happens, and of both the perpetrators and the victims.

When I was growing up in what was then regarded as a fairly rough area of Dublin, there was always a fear that you might get beaten up by gougers. But the gougers had to contend with factors that are now absent, the intimacy and informality of the world around them. Because the world was smaller and more local, there was a good chance that, if someone attacked you, you would know who they were and where they lived. And that knowledge was combined with the possibility of rough, informal justice.

Before kicking you around for their pleasure, the gougers had to reckon with two probabilities. One was that, even if you were small and puny, you might well have neighbours, relatives and friends who were not. Retribution was (and still is in many working-class areas) likely to be swift and brutal. The other probability was that, if the victim's extended family did not exact revenge, the Garda would.

Deplorable as it may have been, and unacceptable as it would now be, the fact that a big garda would invite the frequent offender into the local station for a friendly chat and a few hard digs certainly had an effect.

One of the reasons, then, why unprovoked attacks have become more common is that the attackers have good reason to believe that they will get away with it. They have, in the far less intimate Ireland of today, a much better chance of being anonymous.

The Garda, in general, has neither the inclination nor the time for a system of informal justice. And the families of the kind of nice, middle-class youngsters who tend to be beaten up no longer tend to operate an eye-for-an-eye and a kick-for-a-kick system of retribution.

Which raises the other important factors, the nature of the perpetrators and of the victims. What's happening is that the losers are hitting out at the winners. It is not incidental that most of the people who carry out these assaults are likely to be losers in the Irish social system. They've probably dropped out of school early, or moved into dead-end jobs. They've watched others of their own age get exams, opportunities, and rewards.

In the current boom, when the rewards of success are all the greater, being a loser is all the worse. And they opt for the most stupid, ignorant, but at least momentarily, most satisfying response. They do what outgroups have always done in these circumstances, using violence to make their weakness look like strength.

Such people will tend to attack those whom they perceive as different: gays, blacks, foreigners. Much of the current violence is obviously targeted at people who fit, or seem to fit, these descriptions. What has also changed, however, is that, from the perspective of the losers, most ordinary young blokes have also become different.

The reason the broad "crisis in masculinity" explanations are so wide of the mark is that, ironically, most male teenagers and young adults have changed for the better. They are not aggressive. They don't go in for macho posturing. They don't feel the need to hang around in gangs made of up of inadequate people like themselves.

From the perspective of the losers, they represent the worst possible combination of attributes: successful wimps. There is no greater insult to an aggressive loser than a non-aggressive winner, a weakling who is somehow thriving.

What's really redundant, in other words, is not young men, but a kind of masculinity that relies for its validation on the ability to smash someone's face. Only in a gang, kicking a victim on the ground, can those who are stuck with the old way of being a man really feel that they're still on top. The anger that comes from the tacit realisation that this kind of power is really a pathetic expression of weakness heightens the viciousness.

In the short term, the only way to deal with all of this is to develop a kind of policing that substitutes in a civilised way for the old informal threat of retribution. In the long term, the only way to stop it is to change a system that still produces losers whose finest achievement is kicking in the head of someone who's done you no harm.