In some epochs civilisation retreats, in others it advances. But is advancing always better than retreating - and which exactly is which? Is all advance enlightened progress and all retreat benighted regression? Then again, do the terms “retreat” and “advance” apply at all?

What am I talking about?

You would have known if you had been with me in Park City, Utah, last month. The battle for freedom of expression - long the most compelling spectator sport in moviedom - raged as busily as ever in that arena for maverick cinema called the Sundance Film Festival, carrying boldly on from last year’s hullabaloo-raiser, Inside Deep Throat. That, you recall, was a documentary about the naughty things actress Linda Lovelace did to actor Harry Reems in 1972 when a movie about oral sex ushered in the age of hardcore porn. Deep Throat was saluted in the documentary as a seminal shudder in the soul of America, engendering the liberalisms born after Vietnam, Watergate and presidential disgrace. Reems even claimed: “I’m the thread to tell the story of social change in America.”

The fact that we are still arguing about sex in the cinema in 2006 could be construed as either a victory or a defeat for Deep Throat. We cannot stop talking about screen sex: that’s something. Yet we still cannot agree about it: that’s something else.

Two fascinating movies at this year’s Sundance refocused the debate. Destricted is a portmanteau sex film - with no carnal holds barred - directed by seven independent filmmakers. It includes two graphic male masturbation solos directed by Gaspar Noe and Sam Taylor-Wood; Larry Clark’s Impaled, in which a dozen auditioning young men compete for the chance to have sex on camera with a porn actress (cue frank chat, nakedness, then five minutes of coitus non-interruptus); and - the most mischievously imaginative episode - Matthew Barney’s surreal and erotic vignette in which a nude man has a close and tumid encounter with the rotating driveshaft of a 50-ton truck. Imagine a love scene designed by Hieronymus Bosch with help from Henry Ford.

Like Michael Winterbottom’s 9 Songs and kindred films in this millennium’s busy first decade - for “noughties” read “naughties” - Destricted is another hardcore movie knocking on the door of multiplexes.

So are America and the west becoming increasingly liberal on screen? You might think so. Yet two events during Park City’s festival fortnight suggested that the opposite pull at present is just as forceful. Down in the valley a Salt Lake City theatre owner caused a rumpus by refusing to show Brokeback Mountain at his multiplex because of its gay content. And up in Park City, Kirby Dick’s sobering and hilarious documentary This Film is not Yet Rated, one of the festival hits, is an expose of the repressive, cabalistic workings of the Motion Picture Association of America (MPAA), the organisation that for 40 years has rated and classified the US’s movies.

Responding to his own and other filmmakers’ exasperation at this board’s secrecy - they sit in anonymity and refuse to have their verdicts debated - Dick endeavours to “out” the raters. With ingenuity, skulduggery and professional help (a firm of female private eyes) he succeeds. He finds the names, confronts their owners and a little later dumbfounds the MPAA by submitting his own film to them - this one - for classification. He gets a draconian NC17, the ratings equivalent of a blacklisting. Elsewhere Dick gives examples from the MPAA’s history of eccentric, or worse, decisions. As the appointed watchdog of the major Hollywood companies, it has a record of giving studio movies blatantly lenient treatment compared with that meted out to independent films.

I caught up with Kirby Dick and asked him - who better to give me an opinion? - which direction America’s screen culture is going in right now. Should we rejoice at the liberalisation suggested by Destricted? Or should we be dismayed that the love that dare not speak its name is still silenced down in Mormon leader Brigham Young’s city and that - as shown by Dick up here in the mountains - there are even names that dare not speak their names, as they sit in star chamber judgment on a superpower’s moviegoing?

“It’s always easier to look back than to look at our own time and see the directions,” says Dick. “There is more mainstream access today to graphic films like Destricted, even though the MPAA has always been stricter on sex than on violence.” (Why so? “Because studio movies have more violence and they control the system”). On the plus side too: “I’m somewhat heartened that Hollywood is at last attempting to have some political content in its films, that the liberal-utopian cinema we knew in the ‘60s and ‘70s is coming back.”

But the Moral Majority and religious right, empowered today as seldom before, are there in force to check the pace of any radical renaissance - aren’t they? Dick is sure about the impetus of counter-revolutionary conservatism, less sure of where it comes from.

“I think the religious right is a distraction that serves the Hollywood corporate interest. Yes, the religious lobby is important. But if the battle lines can appear to be drawn in this country over the war of ideas in the media, and not over the media conglomerates themselves and the way they rule the studios and TV companies, then that’s in the interest of those conglomerates and it’s much more serious. That’s why we go to war too. Not for religious reasons but for economic ones.”

He points out that he could not get funding for his own film from any major studio or company. They all saw trouble in attacking the MPAA. It was eventually financed by IFCTV, a small company with no conglomerate connections.

So in the macrocosm of Hollywood, it seems, the defences are still up - impregnable and barely modified - while in the world of independent cinema, as Sundancers can see, directors are extending Freedom Road every year.

We festival folk are certainly getting used to Freedom Road. In some ways the most encouraging aspect of Destricted is that it was not the hottest ticket in town. The press show was medium-full and several people left during the boring bits (which include Sam Taylor-Wood’s interminable onanistic essay in Death Valley and Marina Abramovic’s risible “Balkan Erotic Epic”, a sort of blue-movie homage to Greek director Theo Angelopoulos.

But when sex on screen becomes just another viewing chore, isn’t that a good thing? When we cease overreacting to eroticism, maybe we are ready to treat it creatively, imaginatively, thoughtfully. The worst that can be said of the MPAA or of Larry Miller, Salt Lake City’s homophobic cinema owner, is that they retard the process whereby audiences get past the rarity-value titillation. They slow the progress, surely inevitable, towards an acceptance that will beget fresh views, perspectives and discourses on the phenomenology of sex.

The most educative encounter I had in Park City - simultaneously charming and chastening - summed up the whole business. For whom should I run into near the festival’s close but Harry Reems. The Deep Throat star, once the biggest male porn actor in the world, is now a Park City realtor. Last year Reems briefly rallied to Universal Studios’ request that he help publicise Inside Deep Throat. But it was clearly a labour of reluctance.

“I spoke about Deep Throat when they asked me. But I’m married now, I own my own business, I converted to Christianity. I’m a trustee of my church, I’m seventeen-and-a-half years clean and sober of alcohol, and it’s not a part of my life to speak now and I don’t think I have anything of value to add to what you’re doing.”

This was discouraging, but I am a journalist: I don’t take goodbye for an answer. I wanted to ask Reems how he reacts to the way films such as Destricted have begun to legitimise and normalise the kind of cinema for which he was once criticised and nearly - dare one use the word? - martyred. In the mid-1970s he came close to going to prison along with Deep Throat’s other obscenity-law transgressors.

“I don’t know that mainstream films have become more explicitly sexual. Certainly there’s more eroticism. It’s a product of the times. But films are more aggressive today in general, there is more violence and horror and sexy comedy. But I’ve stepped back from that, it’s been good for me to retreat into a private life.” He adds that he didn’t settle in Park City, all those years ago, in order to be near a film festival. “I first came up here with skiing friends. It seemed such a quiet, quaint little town 30 years ago. I said to myself, this is the place I’d like to hang my hat and live the rest of my life. And I’ve made my dream come true.”

As he says, he also found God, conquered alcoholism and settled into family life. For half a second I almost envy him. He makes me wonder why I spend half my life gallivanting around film festivals courting encounters with the world, the flesh and the devil. Then I come to my senses. I realise that chaos is where I want to be and where every self-respecting film critic should be. Not for the first time I think of St Augustine’s prayer and offer up my own paraphrase. Give me a chaste and contrite life, Lord, away from the feverish task of monitoring screen freedom. But not yet.

Nigel Andrews is the FT’s film critic.