Can a work of art be separated from its creator? The question that has engaged some of our greatest philosophers is soon also to engage a Channel 4 studio audience, which is to be presented with works by such artists as Hitler, Eric Gill and Rolf Harris. (Decisions will be mediated by Jimmy Carr via a hammer.) Before we get to the show, over which much outrage has been generated, I want to advance a theory. My answer to this question is that you can quite easily separate art from its creator – as long as the art is bad. Hitler’s postcard watercolours are perfectly safe to consume as there is nothing of him in them. They might have been created by any number of sentimental daubers who failed (twice) to get into art school. When art is good though, the artist has transferred some of their soul into it. They cannot help but reveal themselves. Gill’s stuff is very dangerous. So it is with any number of great but corrupt artists. Paul Gauguin was a paedophile who took underage Tahitian girls as his sex slaves; his paintings invite the viewer to join him in gazing lustfully at these same teenagers, naked and in sexualised poses. Caravaggio, genius and murderer, produced art that makes violence beautiful. His bright spurts of blood and clear fascination with the expression on a dying face give you a taste of what it might be like to want to kill someone. He converts his audience into, at the very least, morbid rubberneckers. Salvador Dalí’s raging narcissism and cruelty to animals and people is imprinted deeply on his art. His famous short film Un Chien Andalou, written with Luis Buñuel, shows a closeup of a woman’s eye being slit open with a razor and invites us to enjoy the spectacle. It is an act of persuasion. This is inevitable. What separates good art from bad is that good artists say what they really mean. When we talk about genius we are not describing technical skill or the labour of construction, block by block. We mean something more like inspiration: a dart of instinct straight from the soul on to the canvas. The darkest urges of a great artist will, of course, echo in their art. And the self-justifications of the criminal or pervert – that everyone secretly shares their tendencies – will be channelled through their works. Great art is great because it has the power to corrupt, should that be the artist’s wish. It is dangerous. Bad art, on the other hand, is very safe. It thoroughly obscures the soul of the artist – nothing is revealed at all. A thick layer of plexiglass cliche lies between the soul of the artist and the viewer so that no darkness can seep through. In fact, this insulating property is so integral to the genre that it has often been put to a practical purpose: fascists tend to promote and surround themselves with bad art, now known as “totalitarian kitsch”, because it helps disguise them from themselves. There are tales of brutal dictators weeping at sentimental films after a hard day’s genocide. This throws up a bit of a problem for modern moralists, not to mention gallery curators. Current sensibilities demand that our artistic heroes be good people too: seeming to endorse the “problematic” ones, even by discussing them, appears newly risky. This explains some of the outraged reaction to Channel 4’s show Jimmy Carr Destroys Art – which might have delighted audiences in the 80s and 90s. But we have also been brought up on the idea that all great art should be revered. (That explains the other half of the outrage to the show.) Witness the outcry after a pair of climate change protesters threw soup on the protective glass surrounding a Van Gogh painting last week. The picture was unharmed but the justifiably mocking, negative reaction said more about the ridiculous, self-important stunt than anything else. So how do we deal with great art by bad people? The solution that we have tended to reach for in recent years is that art is essentially “harmless”. We can consume the artwork of corrupt people and it will not touch us. That accompanies a similar modern urge to see all great art and literature as “improving”. Judges have taken to prescribing criminals reading lists, as if all books, from Lolita to The Picture of Dorian Gray, were written with the express purpose of turning us into law-abiding citizens. But this does art a disservice. To treat art as harmless is to fail to take it seriously and reduce it to mere decoration. If we want to argue that some art can be good for us, we need to consider that some can also be bad for us. How do we deal with immoral art? It’s still a question worth grappling with. Martha Gill is a political journalist and former lobby correspondent