And what's so wrong with Marlboro Men in love?

US: The two old gents next to me were all set up for an afternoon at the pictures, with giant bags of popcorn, half-gallon cups of soda and a determination to chat all the way through Brokeback Mountain.

But after a few admiring murmurs at the first sight of Heath Ledger and Jake Gyllenhaal, my neighbours went quiet and by the time the film ended they were sobbing, one clutching the other by the arm.

Gay commentators have welcomed the success of Brokeback Mountain as a breakthrough, a sign that a mainstream American audience is ready for a story about love between two men. But the film itself and the tentative style of its public release also highlight how much remains to be done by the gay movement and how far the United States has fallen behind Europe in the struggle for civil rights.

Based on a short story by Annie Proulx, Brokeback Mountain is about two cowboys, Ennis Del Mar and Jack Twist, who fall in love while herding sheep in Wyoming in the summer of 1963.

"You know I ain't queer," Ennis tells Jack after their first night together.

"Me neither," says Jack.

When summer ends, the men return to lives elsewhere but, although they each marry, they can't forget one another and meet regularly over the years for "fishing trips" during which no fish are caught.

Jack thinks that he and Ennis might some day buy themselves a ranch and settle down, but Ennis remembers his father showing him as a boy the castrated corpse of a man suspected of being gay. "This thing gets hold of us at the wrong time and wrong place and we're dead," he says.

For some young gay men who have seen Brokeback Mountain in America's big cities (the only places it has yet been shown) the film is a period piece portraying a remote era before liberation. But for many others, the anguish of Ennis and Jack's doomed love is more familiar than the flippant confidence of the gay characters in Will and Grace or the presenters of Queer Eye for the Straight Guy.

It's not only in rural areas that coming out requires great courage: gay liberation has also passed by hundreds of thousands in America's inner cities, particularly in ethnic minorities.

If Ennis and Jack were African-American, they would be described as being "on the down low" - secretly having sex with other men but not identifying as gay.

Some black activists blame the "down low" phenomenon for the disproportionately high level of HIV in the black community, although there is little evidence to support the theory. Derided by many gays for their failure to come out, men on the "down low" must also face the guilt caused by the misery their deception can bring to their families.

But in his book Beyond the Down Low Sex, Lies and Denial in Black America, black, gay commentator Keith Boykin explains why coming out can be so difficult for black men.

"Most black men grow up in a world where we are feared, despised and distrusted. We respond to that environment by creating a safe space of our own, but for those black men who are not heterosexual, their sexual orientation can be an obstacle to their full acceptance in their own community.

"Since they already face prejudice as black men, they are reluctant to acknowledge their sexual orientation and take on even more prejudice because of whom they love."

As the home of the modern gay liberation movement, America was in the vanguard of the campaign for civil rights for more than 20 years while Europe struggled to shake off discriminatory laws such as Germany's Paragraph 175, Britain's Section 28 and Ireland's complete ban on homosexual acts.

Everything has changed during the past decade, as one European country after another has approved gay partnership or marriage rights and anti-discrimination laws.

Opinion polls show that most Americans favour gay partnership or marriage rights, too, but Christian conservatives have mobilised successfully to block each attempt to introduce them.

The Christian right has, for the most part, held back from criticising Brokeback Mountain, although one religious commentator squealed that "Hollywood has now raped the Marlboro Man".

Perhaps the conservatives are holding their fire because, like most people, they can't think of anything unkind to say about the idea of two people who, far from making a "lifestyle choice", want nothing more than to love one another and be left alone.

As Jack puts it after his first night with Ennis: "Ain't nobody's business but ours."