Extremes are shocking. But they are also, by their nature, easily isolated as beyond the scope of quotidian experience. Ian Watkins, the former singer with Welsh rock band Lostprophets, this week admitted to the most ghastly child sex offences imaginable. It's easy to put Watkins in a box – or a cell – marked: "Beyond human comprehension." Or, at least, it should be.

But a report, If Only Someone Had Listened, published this week by the Office of the Children's Commissioner for England, says something different. In her foreword, the deputy children's commissioner, Sue Berelowitz, states: "The fact that some adults (usually men) rape and abuse children is generally accepted." She's right. Society may abhor the individuals who commit such crimes. But it is indeed "generally accepted" that such individuals exist, and in some numbers.

Berelowitz points out the obvious – that this formerly taboo subject is now far from taboo – in the service of highlighting another taboo. She continues: "There is, however, a long way to go before the appalling reality of sexual violence and exploitation committed by children and young people is believed."

The report, the result of a two-year inquiry, goes on to describe gang-afflicted areas in which "the level of sexual violence and the types of violence inflicted are comparable to how sexual violence is used in war-torn territories". Even when gangs are not involved, the report claims that among young people more generally, attitudes to those who are sexually exploited and raped are far from sympathetic. "The victim, usually a girl (but boys are victims too) is invariably blamed for their own assault," the report warns. "They should not have gone to visit the boy; should not have worn a tight top; should not have had the drink; have 'done it before' so have no right to say no." It's a depressingly familiar victim-blame list.

The report mainly concerns itself with finding structured ways in which agencies and services can intervene to help sexually exploited children and those at risk of exploitation. And that is, of course, of great importance. But there's a disturbing societal context as well, chillingly summed up by Matthew Reed, of The Children's Society: "This report shows that there are particular problems with attitudes towards teenage girls, both from professionals and from their peers."

This rings true. Exploited girls tend to end up isolated from everyone, male and female, young or old, except their abusers, which only serves to give their abusers more power. There was outrage when a judge described a 13-year-old as a "sexual predator" and let a 41-year-old paedophile walk free from court. But how many times in recent years have paedophile rings been uncovered, having run undisturbed for years because female social workers didn't feel able to intervene in the "sex lives" of children?

A couple of years ago, a Canadian psychologist, Tracy Vaillancourt, published the results of an experiment that she claimed showed that "slut-shaming" is hard-wired into the female brain. No one appreciated her efforts much. But her findings, backed by further research, have now been published by the Royal Society, in its peer-reviewed journal The Philosophical Transactions of the Royal Society (Biological Sciences). They're worth taking note of.

Vaillancourt's experiment was pretty basic. Eighty-six women aged between 20 and 25 were secretly videotaped after being told that they were taking part in a study about female friendship, and paired with another woman. As they were waiting for proceedings to start, a third women went into the room, dressed for half of her visits in casual clothes with her hair tied back and the other half in plunging top, short skirt and long blonde tresses. No one commented on the casually dressed woman at all. But almost all of them were actively critical and hostile towards the same woman when she turned up looking "sexy". I suppose women could simply deny that they'd ever encountered such behaviour, let alone indulged in it. But that would be a shame, because people can't change what they don't acknowledge.

Vaillancourt calls this behaviour "intra-sexual competition strategy" and says that it is most conspicuously present between the ages of 11 and 25. Vaillancourt says the behaviour is rooted in the fact that women are the "higher value gender". It's more important for women to stay alive than men, so that they can have and care for children. So women avoid physical aggression and "have had to evolve less risky strategies to compete for preferred mates and devalue their competitors … We exclude females from our peer group, we spread rumours about that person, we suggest they're promiscuous; that kind of thing."

Now, this is, of course, no excuse for male behaviour. But it does help to explain why cultures around the world repress female sexuality so successfully. Female collusion in the sexual repression of women by males is typically explained by feminist theory as motivated by fear of men, or failure to understand and resist "the patriarchy". Vaillancourt's ideas suggest instead that women have historically colluded because it served their own evolutionary advantage. I always suspected that men couldn't possibly be capable of such universal success in subjugating women all by themselves.

It's significant, I think, that this sort of behaviour starts in early adolescence and tails off when women reach the age of about 25. Rejection by their female peers because they are seen as "sexy" can only drive young girls towards people who appear to be interested in that, thus compounding their vulnerability. With an understanding of what's going on, older women are going to be much more capable both of educating young girls about the dangers of indulging in this sort of female aggression towards other females, and of spotting those who are likely to be the most vulnerable to exploitation.

Of course, Vaillancourt, and those who find her ideas useful, will continue to be regarded as the enemy by "victim feminists", who wish to simply blame men for all of women's problems, without spotting the irony in that position. Feminists already defend the right of women to dress as they please, to have the sexual lives that they choose, and to be able to live without fear of sexual violence, even if they've had a drink. But maybe it's time to acknowledge not only that women in the past have rejected such freedoms themselves, but that to do so is a natural but unattractive female tendency.

In her foreword to If Only Someone Had Listened, Berelowitz says: "We have found shocking and profoundly distressing evidence of sexual assault, including rape, being carried out by young people against other children and young people. While we have published chilling evidence of this violence in gang-associated contexts, we know too that it is more widespread than that. This is a deep malaise within society, from which we must not shirk."

The behaviour of adults such as Ian Watkins may indeed be inexplicable. But the suffering of the children in the Children's Commisson's report is surely explicable. Perhaps it is the result of an adult failure to understand how isolated, alone and vulnerable an adolescent girl can be. And that should not be something that's hard to understand at all.

• This article was amended on 30 November 2013 to remove an incorrect reference.