WHO wouldn’t want a friend like Dame Judi Dench? Probably the best-loved actress in the country, she has made an impassioned plea not to airbrush people like her good chum Kevin Spacey, or even Harvey Weinstein, out of sight and mind.

“Are we going to negate ten years at the Old Vic and everything that [Kevin] did – how wonderful he’s been in all those films?" she says. "Are we just not going to see all those films that Harvey produced?”

And, while she does not dismiss the seriousness of the crimes they have been accused of, she staunchly defends their work, and its right to ongoing appreciation. “You cannot deny somebody a talent,” she says in an interview with the Radio Times. In so doing, she has struck a long-overdue blow for the integrity of art, regardless of how sordid or nasty the person who made it.

It is a conundrum audiences, viewers and readers have often had to struggle with. Can you look at a Salvador Dali painting without remembering how cruel he was to his womenfolk, not to mention animals? Enjoy a Maigret novel despite knowing that no housemaid or waitress within reach of Georges Simenon’s grasp was safe? Or listen to Wagner’s or Phil Spector’s musical genius without caring about their fascist views or crimes? Once you start, the list of writers, painters, musicians, thespians and all the rest of the creative throng who have lived what you might demurely call “chequered” lives is never-ending.

And yes, it’s hard to deny that knowing of someone’s atrocious acts does stand between us and the art. The creator is always present, becoming part of the experience. But this awareness should deepen rather than detract from the understanding of the piece. As Dench insists, “We shouldn’t judge culture by the morality of its creators.” If we did that our walls would be blank, bookshelves half-empty, cinemas and theatres shrouded in darkness. The complex psyches of some artists are plainly the wellspring for their performance. There is even a school of thought that suggests the tormented or immoral activities of such individuals actively feeds their work.

At that point, however, I lose all sympathy. Nobody is above the laws of decency, and everyone knows when they have crossed a line, whether it’s criminal or not. The cliche of the tortured artist, allowed free rein to behave as he likes because his genius justifies everything, is completely bogus. Effectively it is to argue that an artist is like the Minotaur, a monster whose appetite needs stoking with living prey. Frankly, it is a pathetic excuse, as if the artistic label allows someone a degree of moral leeway forbidden to a decorator or accountant.

That, of course, is not what Dench is suggesting. Nor is it the view of any of us who think it’s necessary to make the distinction between the artist and what they produce. Whatever the outcome of the case against him, Spacey has been a stellar actor, and to deny that, to write him out of history, is not only wrong but sinister. As viewers we can choose to watch him or not. A director can decide not to employ him, or an actor not to work with him. But let’s not be so squeamish we can hardly speak his name, or turn to him on Netflix. When we go down that road, we become like Henry VIII, throwing folk into the Tower for daring to mention Anne Boleyn, whose head he chopped off.

As we set up a hue and cry over Boris Johnson’s private life, or that of any politician found fiddling expenses, fathering an extra-marital child or groping a colleague, is there a double standard at play? Nobody would deny that it is acceptable and even praiseworthy to visit an exhibition of the murderer Caravaggio’s paintings, or read the adulterer Charles Dickens’s novels, or watch the plays of Jean Genet, who was jailed for theft and prostitution. Yet the slightest hint of a misdemeanour among our MPs and MSPs is followed mercilessly, like a pack of hounds catching scent of a fox. Is it not better to treat public figures as if they were Old Masters, judging them by their output, not their ethics?

If only we could. The problem is, as Boris Johnson knows all too well, in politics the personal is political. Unlike the arts, democracy is founded entirely on trust. Politicians are elevated to power on their promises and their probity. We might worry, with good cause, that this contract has been fatally eroded in recent years, but the principle remains enshrined. If someone is discovered to be violent or unstable, unfaithful, reckless or a liar when behind their own front door, it does not augur well for their professional, public persona. Indeed, the very fact that a prime minister lives with his or her family – nominally at least – at No.10 Downing Street, or a First Minister in Bute House, is tacit acknowledgement that for so long as they are in office their entire life is open to public view, and justly so.

Nobody in their right mind would have thought to ask Lord Byron to babysit their teenage daughters, but you should have no doubts about the trustworthiness of the PM in that regard. You probably wouldn’t have given the notorious scrounger James Joyce the password to your savings accounts, but you know that in Nicola Sturgeon’s or Theresa May’s hands, it would be completely safe. In other words, character and integrity should be evident in everything a politician does.

This is not to say it’s okay to probe into a politician’s private life as if conducting keyhole surgery. Michael Gove and all the others who say they have the right to privacy, and to a pre-parliamentary existence, are correct. To expect our leaders to be saints is plainly ridiculous. But when evidence of corruption or deceit, rank hypocrisy or simply a chaotic home life comes to light – as, for instance, when the police are called because of a woman screaming – then it matters. It cannot be swept under the carpet. While art comes from the imagination and kicking at convention, running the country demands discipline. It requires decency, truth and, most importantly of all, abiding by the common rules of good behaviour.