Yasmin Alibhai-Brown: How did sexual relations become so brutalised?

I met up with a close British Asian friend in a local Thai restaurant for lunch. On a nearby table sat a pandemonium of women. That collective noun is usually used for noisy parrots and so these were – excited, repetitive and raucous as they slurped their hot Tom Yum soups and glugged down beer. They were in their late twenties and well groomed. They looked like bank cashiers, shop assistants or local authority workers.

Through the entire one and a half hours they chortled and yakked about fab sex toys. My friend's toffee-coloured skin turned a shade of purple as the talk got racier and more graphic. Four young men next to us laughed out loud for a while and then turned vicious, told each other what they would like to do to the "dirty bitches" who obviously had never been "f***ed senseless" by real men.

Our lunch was despoiled, but hey, we got to hear about, for free, dramatised scenes of modern sexuality – dirty talk, instrumentalised bodies (in all senses), violent male imaginings, and the unutterably dismal severing of sex from love and affection.

Louise Mensch has been up and about revealing the savage misogynist invective and rape threats whizzed over to her by unseen internet trolls. Many women in public life, including me, are similarly hounded daily. (My stalkers are particularly keen on female genital mutilation.) We all assume that these abusers are cowardly, only able to intimidate because they are anonymous and that it is all in their dingy and damp little minds. Not so. Those men at the restaurant felt no qualms at all about freely sharing their most perverse reveries. I can't describe them here without a sense of violation. Of course that makes me laughably prudish and uncool.

Every civilisation, every age has been fascinated by and written about sexual skills, tricks and desire, including sadomasochism – think of the Kama Sutra, Justine, or The Story of O. I even have an old erotic manual written by a randy old Muslim sage. Quite a turn-on, I can tell you. But somehow, without any of us really noticing, secret human fantasies, internal monologues that can excite and ignite desire were turned into masculine weapons of virtual terrorisation and now are altering sexual norms and expectations, absolutely for the worse, perhaps forever. When sex became freer and less socially controlled – a necessary, progressive change – it sadly became devalued. Many in the West seem to have got bored with it. Too much, too soon, too easy.

On Thursday night you can watch More Sex Please, We're British ( Channel 4), featuring toys and bondage gear you can order online, and "sexperts" to instruct you on DIY and/or sexual domination. Maybe IKEA will soon have its own sleek line, and join the supermarkets which already sell such pleasuring items. Middle English small towns come top in the league table of sex aid purchasers. Something to break the boredom, perhaps. A Relate counsellor warns that efficient, mechanised orgasms could alter the female brain, making it less receptive to human hands and other bits.

It is yet more evidence of the instrumentalisation of intimacy and hardening of sexual relations. And of brutalisation too. Lurid accusations and new cases pile up against Dominique Strauss-Kahn, once head of the IMF. What I find most striking is Kahn's genuine bafflement that he is damned just for his libertine tastes, for referring to women he allegedly ordered up for sex as "equipment" and "material" and for some "rough" sex with prostitutes, two of whom now claim he hurt them. Meanwhile, that other ladies' man, Silvio Berlusconi, is on trial for some of his unsuitable pastimes. Witnesses say he had a taste for "sluts" from South American slums who spoke no Italian. He too thinks he did nothing wrong.

The women are willing, but that only seems to provoke aggression. The men at the restaurant wanted females demeaned, conquered by macho strength, as one said, "to show them who's boss". Around universities, female students' drinks are regularly spiked with drugs and we know figures for sexual assaults and rape are appallingly high. And yet many of today's women not only participate in female debasement, they validate, even glorify it. Cutesy Amanda Holden was on TV last week fessing and chuckling that she had seen the secretly filmed tape of X Factor judge Tulisa Contostavlos having sex as a teenager with her boyfriend. Would, she, I wonder laugh if her own daughters were thus objectified?

And then along comes Fifty Shades of Grey, by EL James, a nasty S&M trilogy, already a best-seller, described as "mommie porn". The heroine, 22, knowing and "strong", chooses to surrender to an older man, to welcome pain he inflicts and his total control. And we naively thought young women wanted equality in the workplace, society, home and bedroom. Violent sex is now actualised and merchandised, spread through society, impacting on loving sex, marriage, family life, respect, women, and men. One day they will look back to our times, as we do to the orgiastic, unfeeling Romans, and wonder what happened and why.

y.alibhai-brown@independent.co.uk