It is open season once more on randy American presidents. In a forthcoming TV documentary on Bill Clinton's sex life, Marla Crider, a former colleague (and, of course, lover), revealed that women were "totally mesmerised... it was like bees to honey".

The womanising days of another priapic president, John Kennedy, have been recalled in a book called Once Upon a Secret, in which Mimi Alford tells the story of her own White House affair when she was a young and, briefly, virginal intern.

It almost goes without saying that a mini-hurricane of disapproval has attended Alford's book. One reviewer described her as a Barbie doll and Stepford wife, while Kennedy emerged "a deeply unpleasant individual, a liar and a hypocrite, vain and arrogant in equal measures".

Even The Spectator, not noted for primness, asked in a headline, "JFK: The Nastiest President of the Twentieth Century?"

This superior moral position is not shared by Alford. The closing scene of her book describes a visit to Kennedy's grave at Arlington Cemetery with her second husband. Standing there, she silently mouths the words, "Thank you".

This approach to past misbehaviour plays very badly these days. We know precisely what we are supposed to think. A powerful man who takes a 19-year-old intern's virginity and subsequently involves her in tacky sexual behaviour is a brute and villain.

The woman, whatever she might say, is the victim. Yet any adult sexual being will know that this version is a nonsense, a comforting fairy-tale which takes no account of actual human desire.

It was sex, for heaven's sake. Does it really still need to be spelt out that there is a connection between sex and power?

The real reason why the reaction to Mimi Alford's book has been so poisonous is that her account is clear-eyed and unashamed. Now 69, she looks back without bitterness or resentment towards her employer or her own racy young self. The affair was what it was. This kind of honesty makes the modern moralist uneasy. "Ms Alford seems to have little idea how badly her stories reflect on herself," scolded The New York Times reviewer Janet Maslin.

Behind the disapproval, there lies a double standard. In the world of rock 'n' roll, it has been accepted for decades that fleeting, undignified, hero-to-fan sex acts occur. It's understood that men and women, under the right circumstances, will behave in ways which, described years later, might seem excessive or indecorous.

The argument is that those who work in politics should operate by a different code.

Perhaps they should. If Kennedy was not with Alford during the Cuban Missile Crisis, maybe his judgement would have been better. Or it might have been worse. No one has convincingly argued that Kennedy's randiness - or Clinton with his mesmerised women - made them worse presidents. It is our own age, this great moment of bogus moralising, which has the problem. We should be grown-up enough to admit that often the connection between power and desire has nothing to do with bullying or victimhood. It just happens.