I wonder what would happen if an artist revealed that in an official portrait of George W Bush, he painted a dark shadow representing the Iraq war.

Actually I know what would happen. Fox News would lead a conservative uproar that condemned this insidious piece of unpatriotic propaganda. I can hear them now.

“Who runs the National Portrait Gallery – Isis?”

But former Democrat presidents who never started major wars in the Middle East are fair game. Painter Nelson Shanks has attracted amusement and kudos with his revelation that he depicted the shadow of Monica Lewinsky’s stained blue dress in his official portrait of Bill Clinton for Washington DC’s National Portrait Gallery. You can bet Fox News won’t be complaining about this. It is, after all, common knowledge that Clinton has a “stain” on his character.

Never mind that he presided over an economic boom with a zero deficit, while more recent US administrations have struggled with crisis and debt. Never mind that if he had still been president in 2001, America’s response to the horror of the attacks on the World Trade Center and Pentagon would surely have been more judicious. Clinton had sexual relations in the Oval office, and that casts a “shadow” according to Shanks.

In reality, on his political record, Clinton is one of the least “shadowed” American presidents. He deserves more respect.

So who is Nelson Shanks, anyway?

He is a deeply conservative artist – speaking aesthetically you understand. Shanks believes in “classical realism”, a consciously old-fashioned and pedantic painting style. His paintings – as you can see from his portrait of Clinton – are meticulous attempts to render visual appearances with none of those expressive experiments you get from avant gardists like Lucian Freud. He is skilful, but not imaginative.

Shanks is particularly proud of having portrayed Princess Diana, Pope John Paul II and Ronald Reagan.

Unfortunately, the world of traditionalist art is all too likely to coincide with, let’s say, old-fashioned politics. If you build a fortress around your art from which you exclude all noxious modern influences, it is likely you may also reject society’s liberal poisons. I don’t know how Mr Shanks votes. But it seems strange to me to single out Clinton as somehow not deserving a fully respectful portrait.

In his novel The Human Stain, the great Philip Roth reimagined the Lewinsky story as a paranoid convulsion of American morals in which a man’s complex humanity was held against him – a kind of modern Salem witch hunt. You don’t have to believe his sexual conduct was OK to think it is a bit rich to see Clinton as a villain in a world that contains George W Bush and Tony Blair.

Tragically, Blair seems to have let his own suspicions of Clinton’s moral character delude him about Bush. Although he and Clinton worked well together, he reportedly came to think Bush was the more decent man. What a mistake. The world is scarred by the decisions of George W Bush. Only a dress is stained by Clinton’s supposed sins.

Oh, what a hero Nelson Shanks is, to vilify a president who in his time made America somewhere to look up to, rather than away from.