Truly, nothing says Christmas like a footballer-party rape allegation. It's getting so Pavlovian that the first story suggesting one guest might have enjoyed herself rather less than the others at some club's festive bash has become as evocative as the smell of mulled wine or wilfully spun reports suggesting the Muslims are stealing our Christmas.

Facetious? Most of the responses to the fact that a 19-year-old Manchester United player has been accused of raping a 26-year-old woman at the club's Christmas party early on Tuesday have been about as nuanced. They have run the gamut from "footballers are lawless scum" to "the girls are no better: they all deserve each other". There were some "she probably made it ups" in there, too, and maybe the odd "women are just meat to these beasts".

Yesterday further revelations about the party surfaced. One "very drunk" woman was "roasted" by five or six men, according to another guest, who told a newspaper that "I asked her if she was OK and she said, 'Yeah, why wouldn't I be? They said I was a great shag.'"

There will be people - some would even count themselves as third-wave feminists - who can read that statement and accuse anyone who feels the vaguest sense of unease about it of being straitlaced, or repressive of this woman's natural sexuality. These people like to think of themselves as sexual cognoscenti - a bedroom version of those television chefs who tell you they always get their truffles from a family supplier in Puglia and assume you'll do the same. For their bondage tips, they go to the Marquis de Sade in the original French.

If they're that smart, though, they should appreciate that not everyone indulges in these things with quite the same degree of consequence-free delight and rationalised abandon as they do - and it's inverse snobbery to pretend that it is so.

And so to a vexing riddle of our times. Namely, if six footballers can have six girls each, why do they only want one between them? The answer is actually incredibly simple (and has nothing to do with repressed homosexuality). It might be partly that they enjoy team activities and it's a kind of extended goal celebration, but it is primarily because that is what they see in porn. And porn is screwing up sex. Not sex in relationships, but the kind of casual sex in which it would be nice to think people could indulge in a mutually enjoyable, non-exploitative fashion. In this context, footballers are not qualitatively different from plenty of other young men, it's just that being regarded as demigods makes it easier to act in this way.

Several years ago Naomi Wolf pointed out that the proliferation of porn, particularly on the internet, was the way most young men and women were now, in effect, taught about sex - "what sex is, how it looks, what its etiquette and expectations are". It had a significant impact on the way they interacted. She wondered whether all the sexual imagery around represented the true liberation of sex, or whether "the relationship between the multibillion-dollar porn industry, compulsiveness, and sexual appetite has become like the relationship between agribusiness, processed foods, supersize portions, and obesity".

No matter where you stand on it, porn has undoubtedly skewed many young men's expectations of sex, and many young women's sense of sexual obligation. The marvellous website jezebel.com touched on this theme recently, having identified an experiential trend among the staff's acquaintances. Several of these women had been on a first date, ended up sleeping with the guys, and the men had ejaculated on their face without asking. The reader responses were revealing. It transpired that lots of people had had this surprise experience, and while there was debate about whether the act referred to was rank misogyny or something you could truly love, there was unanimous concurrence that it should be on the "have to ask first list" - and that the presumption even in a few people that it wasn't signified a shift in popular male imagination. Several younger readers wrote in saying that they found men their age were so conditioned by porn that "they don't think sex is 'good' unless it's somehow fetishy".

Now, either these guys were just borderline rapists, or - way more likely and way more scarily - they simply didn't know any better.

It would be nice to think we could reclaim the right to say people don't know any better without being accused of snobbery, because the longer we allow the argument to be short-circuited in that fatuous way, the longer the debate remains buried. And there are plenty of questions, wherever you stand. Is this the only sexual liberation we're going to have, or are we due another rethink? Are both genders having better sex than they did 10 or 20 years ago? Could it be that women who queue up outside a hotel just itching to be told they are "a great shag" by an assortment of footballers have bad sex most of the time? If we placed more emphasis on addressing these issues, would there be fewer of what we might, with immense charity, call "misunderstandings"?

marina.hyde@theguardian.com