Sexual intercourse began, Philip Larkin famously declared, “in nineteen- hundred-and-sixty-three, which was rather late for me/ Between the end of the Chatterley ban and the Beatles’ first LP”.

It would certainly have seemed late to Alfred Kinsey, whose famous report was finally closed in 1963, seven years after the death of its author, a man who talked about and probably indulged in more sex than anyone from Casanova to the Marquis de Sade.

Almost half a century after Kinsey’s death in 1956 — possibly brought on by sexual exhaustion — a film of his life starring Liam Neeson has rekindled the battle he ignited for the soul, or at least the libido, of modern America.

The radical right has called for hellfire damnation on anyone involved and even liberal critics have called it schmaltzy hagiography. There is no doubt that the so-called father of the sexual revolution was more than a little in love with his job. As his wife Clara, with whom he presented the public picture of the wholesome American family, famously commented: “Alfred is so busy. Since he got interested in sex, I never see him.”

Kinsey, the Harvard-educated entomologist whose first obsession was the study of gall wasps, lived the outward life of the stolid scientist, insistent that his scandal-provoking, bestselling studies of human sexuality were the product of purely statistical research.

In reality he was a bisexual libertine who thought the only abnormality was abstinence and whose biographer believes that he twisted his methodology to justify — and gratify — his own sexuality.

The fame he acquired was not the sort to gratify his father, a dour Methodist engineering teacher from Hoboken, New Jersey, who banned dates with girls, Sunday newspapers and held the God of Wrath in higher esteem than the God of Love. Alfred, born in 1894, had a repressed, miserable childhood, was kept ignorant of sex and was tortured by his occasional homoerotic fantasies.

The Kinsey Report, as it became popularly known, was two books, the first of which, entitled with deliberately dull scientific sterility Sexual Behaviour in the Human Male, came out in 1948 and the second, on the female, in 1953.

The first book, with apparently scientifically irrefutable evidence collated from thousands of anonymous interviews, claimed that almost all men masturbated, 10% were homosexual, adultery was commonplace and young men on farms had sex with animals. America was knocked sideways.

In a country picking itself up after the second world war and in the grip of paranoia about the cold war, no news could have appeared less welcome, except that it sold its 200,000 print run within weeks and “generated more headlines than the atomic bomb”.

Homosexuality had previously been equated with communism and Congress’s committee on un-American activities was unamused to hear what activities most Americans actually did get up to. Even today the biopic has evoked outrage from sharp-toothed dinosaurs of the new right such as Concerned Women of America which compares Kinsey to Josef Mengele, the Nazi doctor, or Morality in Media, which says that Kinsey’s legacy is Aids, abortion, child abuse and internet pornography.

How did Kinsey happen? His repressive religious parents have a lot to answer for. When Kinsey, the bright young science nerd, married Clara McMillen, a chemistry student, they were so ignorant about sex that they failed to consummate the marriage for several months.

Such ignorance was so common that in 1938 the Association of Women Students petitioned the University of Indiana, where Kinsey had moved from Harvard 18 years earlier, for a course for students who were contemplating marriage. Kinsey, the zoology professor, was asked to co-ordinate it.