I want my artists to be moral heroes

Just five pages into Robert Hughes' new biography of Goya, the reader will come across this sentence: "Artists are rarely moral heroes and should not be expected to be, any more than plumbers or dog-breeders are." This is fairly characteristic Hughes stuff - it carries the suggestion, both exhilarating and mildly comic, that there's nothing he'd like more than to have a bit of a ruck with you.

In fact, Hughes' writing often reminds me of that old Monty Python sketch about the philosophy department at the University of Wallamalloo - in which discussion of Hegel and Logical Positivism is continuously interrupted by the chanting of Rule No 1: "No pooftahs!" Hughes loves art and he loves writing about its nuances and subtleties. He even loves writing about the play of light on a silk dress. But he wouldn't want you to get the idea that there's anything limp-wristed about his enthusiasms. So, every now and then, he invites you to arm-wrestle. Come over here, if you think your received opinions are hard enough.

I would usually pass on the challenge, but this time an accident of timing pulled me up. The recent deaths of Leni Riefenstahl and Elia Kazan had come at this issue from another direction. Many of the obituaries of these two film-makers were a reminder of just what a sizeable prejudice Hughes was taking on - since nearly all of them rehearsed bitter arguments about these artists' moral failings, in ways that strongly suggested that we had the right to expect more of them, given their acknowledged talents. And both of them had suffered subsequently in ways that they certainly wouldn't have done had they been plumbers or dog-breeders. Riefenstahl effectively ceased making films altogether, and Kazan was ostracised by many in Hollywood. So, is Hughes right to say that the expectation is an improper one? Both Riefenstahl and Kazan made choices that would have been problematic for any human being, but was their crime amplified by unreal expectations about their capacity to make the right choices?

One thing you can say right away is that even if there isn't a moral difference between an artist and a plumber, there is a sharp difference between what they produce. If you were to find that your central-heating boiler had been put in by a former SS officer, you might very well be dismayed, but you wouldn't, I think, have it ripped out and start again from scratch. Plumbers who plumbed under the Nazis didn't have the quality of their pipework questioned after the war (indeed, those highly specialised plumbers - rocket scientists - found that their services were highly sought after). Nazi dog-breeders would probably be very good at the job, given that a distaste for mongrelisation is a basic requirement. But Riefenstahl's abilities to thrill were tainted by the ends to which she put them in 1935 and 1938, when she released Triumph of the Will and Olympiad.

Riefenstahl's defence against postwar accusations of complicity with Nazism was an aesthetic version of "I was only obeying orders". The Muse commanded, she implied, and she had no choice. All those shots of Hitler as a demigod, silhouetted against glowing skies, were merely compositional instinct, not political endorsement. Indeed, in some of her interviews, she managed to suggest that it was unfair to expect her to notice what she was making her compositions out of.

She's not the only artist to claim a kind of diplomatic immunity from the general rules. The writer, Graham Greene once famously said, must have "a splinter of ice in the heart". But Greene at least understood that this might involve a conscious sacrifice of human sympathy on the part of the artist - that they might have to become a kind of immoral hero. Riefenstahl seemed to think it entitled her to more sympathy rather than less.

The problem for her was that if we believe the film is acting upon us morally, then we necessarily take a close interest in the morality of its creator. How the water comes out of our taps is unlikely to affect our thoughts about justice or social order, but the visceral thrills of Olympiad - which can stir even the wary viewer - might. What's more, our surrender to a work of art, to its arguments and emotions, inevitably carries with it a kind of hope about its creator.

This was Kazan's problem. Would he have been in nearly as much trouble if he had been a successful director of swashbuckling action pictures, in which a dashing indifference to the common good was part of the appeal? I doubt it. But Kazan had just made On the Waterfront, an extravagantly praised film about moral courage in the face of intimidation. On the Waterfront is an exhortation to the audience to behave better - and while no good art merely sermonises, it's difficult to think of great art that doesn't at some level interrogate the audience about what it truly values. So when Kazan caved under pressure (not from the House Committee on Un-American Activities, as it happened, but from his studio boss and his wife), he couldn't claim that he didn't know what he was doing. The work amplified his responsibility rather than diminished it.

Hughes is right in one respect. Artists are human, just like plumbers and dog-breeders. But his line would be closer to the truth if it read: "Artists are rarely moral heroes, but if their work is any good, we're bound to expect them to be."