To a greater number of enslaved, brutalised women it must have seemed as though the final degrading joke was being played. Reality had been discarded in the space of a headline.

The overwhelming truth of prostitution is grim beyond belief. Yet here was a smiling woman with a passing, self-conscious resemblance to Catherine Deneuve in the Bunuel movie and she was reassembling all the old, exculpatory stereotypes. Dr Brooke Magnanti, “petite, blonde thirtysomething”, as a serious newspaper actually said, was discussing her experiences as “Belle de Jour”, prostitute and author, and she was saying that all was well with her world.

As a sex worker she had been safe, well-paid and guilt-free. She had been looked after by a conscientious agency. Invariably, she had been shown a good time. She had bought herself an education, and hence a career in medical science, with the proceeds. As though to prove how often fortune can smile, Dr Magnanti had meanwhile applied her wits further and blogged, never guessing – for who does? – that her alter-ego’s tales might be worth a best-selling book.

Revealing her “true identity”, Magnanti was careful to concede that her experiences were not typical of the sex industry. Alert readers were left to guess that she had not been lured as a child from some Bulgarian village, raped, beaten, infected, drugged witless and put to relentless work. The specialist in developmental neurotoxology and cancer epidemiology – speaking for herself, of course – had a different message, an old one: prostitution can be glamorous, and some of those male fantasies can be made flesh.

Hence the near-audible howl from the millions of women who know better. Unless Magnanti’s prose embraced the art of fiction, she was the exception, even the exception to the exception. For campaigners and all those who pick up the pieces from the industry with which she flirted, she was statistically insignificant. Yet even if she had not come to harm, and would never come to harm, her confident, ­articulate message to countless young women was actually lethal.

That glittering, silly, soft-focus Billie Piper TV series? It could be you. Merely observe a few elementary rules and discard a few inhibitions: life is a photo-shoot. Magnanti almost made it sound like one of those adverts for jewellery catalogue agents: I made £££s in my spare time! She might as well have been a Lottery winner giving lifestyle tips to a dole queue. Yet because the fantasy of bought sex endures, she filled the airwaves and the newspaper pages for a week.

And that is no bad thing. First, it meant we were reminded, if required, that the common reality of prostitution bears no resemblance to the life Magnanti described. Even those despairing campaigners were given a rare chance to say again that the sex industry depends on murderous brutality, and that the government’s latest attempt at legislation is liable to make matters worse. We heard, too, of the stratagems adopted by other countries, whether in criminalising men, regulating legalised brothels, or refusing to tolerate the trade.

But there was something else. It depends on a simple question: what’s wrong with prostitution? I mean specifically, in itself, of itself. In other words, were it possible to insulate these transactions from crime, disease, drugs, life on the streets, the threat of murder or mere coercion, would the public world still object? If prostitution ceased to be about power inflicting itself on the weak, if it no longer involved ruthless exploitation and sheer slavery, what would “we” think of it?

We would have to think, to begin with, why such a state of affairs has never before pertained. History tells it plain. For every celebrated courtesan with a fancy invented name, in every age, there has been an entire immiserated class of women, disposed of as men saw fit. This implies, beyond much doubt, that prostitution is the way it is, and has always been, not because of a shortage of the lucky, smiling Belle de Jour sorts, but because men make that choice.

It’s called hypocrisy. It’s the politician in the massage parlour; the judge who has no idea that his car has slowed to a crawl; those ministers attending the General Assembly who were, or perhaps still are, the stuff of Edinburgh legend. They make, enforce, commend or applaud the law as though to ensure that there is a law worth breaking, and an illicit thrill to be had. They create criminals for their pleasure. The cliche is antique: the vast ­­majority of prostitution’s customers – and the numbers are vast – are respectable.

That familiar truth need not deflect the question. If there could be no exploitation and no threat of harm, where would the problem lie? Because payment makes sex sordid? A lot of paid work is sordid. Sex is meanwhile central to several of the contracts society endorses. George Bernard Shaw was probably thinking of the men who talk of their “conjugal rights” when he asserted that marriage is legalised prostitution. He meant to provoke, but a sexless relationship would still count, I think, as grounds for divorce, as a deal-breaker.

And let’s be honest, in any case. Do we suppose that every marriage is founded on love? Many marriages are contracted – still a revealing word – on the basis of certain understandings involving, ­variously, sex, the production of children, material goods, status, cash, inheritance rights and more sex. You do not have to be a member of our revered aristocracy, or even our royal family, to understand as much. Deals are done at every level of society, and there is precious little romance involved. Why is prostitution, the essential transaction of prostitution, any different?

Besides, are we not in an age that respects the right of the person? This sounds counter-intuitive, given that the subject at hand is the abuse of women. But that abuse is the very definition of the opposite of choice. Why would so many still flinch from prostitution (male of female) if it involved safe choices, freely made?

Some would point you towards their favourite holy book, but they are, I think, too late. The time, if it ever existed, when reproductive organs could be made obedient to scripture is long gone. Others might say that a freed trade in sex – a good capitalist notion – would tend to undermine the institution of marriage. But the sometimes-and-often-married of our world seem to have knocked away the pillars and the vows without much assistance. That would be true, I think, irrespective of all the sex workers who claim to moonlight as the saviours of marriages.

Society’s last line of argument might be called the psycho-therapeutic. It is less an argument than an assertion, even if it involves beliefs I might happen to share. This says that sex should be “meaningful”, and part of a relationship that is more than casual. It says, in fact, that monogamy, even serial monogamy, is a good idea, and that the instant availability of bought sex puts a damaging countervailing pressure on relationships and families.

Perhaps so. But should society tolerate the horrors of the sex industry? Such appears, after all, to be the proposition: either/or. Either we continue to keep prostitution in murderous darkness, it says, or we risk the stability of the daylight world. Why does that sound like nonsense?

The sex industry is vile because the men who run it and use it would have it no other way. They are not acting out of social conscience. One group wants easy money; the other wants to pay for the chance to use helpless women on command and according to whim.

Dr Magnanti, “Belle de Jour” – who sounds as though she has never seen the bleak film – has provided the trade with a fresh set of glib, glamorous and deceitful excuses. She was lucky. The countless women forced to pretend to play her game will never be so fortunate.

Why not? Because, I suspect, men couldn’t stand to see those women making the free choices, sexual and economic, that liberated prostitution would allow. Sheer slavery is tolerated instead. For the common good.