It never seems to occur to Boris Johnson’s critics that they might damage him more if they toned things down a bit and sounded slightly less pious, moralistic and vindictive.

This is particularly true of partygate. In order to justify going on and on about it, both his political opponents and the feral beasts of the media reckon it is incumbent on them to take a high moral tone, and to demand that Johnson himself resign.

They give us to understand that they are talking about a dereliction of duty which could not be more serious. The Prime Minister made the rules, and then he allowed people in Downing Street to break the rules, after which he misled the House of Commons.

The man is a liar and a criminal, and he must go. That is the general tenor of a lot of Opposition comment, and of many a denunciation by some of our finest columnists.

It can be enjoyable to write this stuff, and also to read it. A warm feeling of self-righteousness courses through one’s veins. How superior one is to the contemptible person in Downing Street who has brought such shame on his country.

These critics look forward to resuming normal service once they can get away from the invasion of Ukraine, an event which demonstrated that in Vladimir Putin, the world beholds a leader who has inflicted unspeakable cruelties on the freedom-loving Ukrainians, and on many other people too.

So long as the invasion of Ukraine leads the news, it is difficult to train the full weight of one’s moral artillery on those responsible for partygate.

But at Prime Minister’s Questions this week, Sir Keir Starmer did devote the last two of his six questions to that topic:

“Talking of parties, the Prime Minister told the House that no rules were broken in Downing Street during lockdown. The police have now concluded that there was widespread criminality. The Ministerial Code says that Ministers who “knowingly” mislead the House should resign. Why is he still here?

Resign! It is the duty of an Opposition to oppose, so one can see why Sir Keir – having for a few weeks stopped calling for Johnson to resign – has now reverted to doing so.

And there is of course a considerable part of the public which is so appalled by the Downing Street parties that it agrees with Sir Keir. To this can be added many who are so angry with Johnson about other things that they will seize any opportunity to try to get rid of him.

But there is also a large part of the public, less reported because its views are less defined and more difficult to turn into a news story, which Sir Keir should bear in mind as he seeks to win hearts and minds, and to build a winning coalition.

“Merry England” is not quite the right term for this more tolerant part of the nation. “Live and let live Britain” would perhaps be a more accurate term for it, though not, I admit, a very catchy one.

Some of us invariably demand harsh penalties for malefactors, and especially for politicians who have erred. But some of us are more easy-going.

“Use every man after his desert, and who should ‘scape whipping?” as Hamlet put it.

Such tolerance may seem, to sterner spirits, disgracefully lax. But the sterner spirits can, in their turn, sound horribly hypocritical.

Have they themselves never broken any rules? Are they so perfect that they are entitled to sit in judgment? Do we not all sometimes stand in need of mercy, tolerance, latitude?

This is not just an argument about morality. It is also a question of political prudence. If Sir Keir and the rest sound too partisan, intolerant, moralistic and punitive, they will repel as well as attract.

The most successful of Sir Keir’s predecessors understood this very well. Tony Blair relates, in his memoir, A Journey, how he used carefully crafted understatement to defeat a succession of Conservative opponents:

“With each successive Tory leader, I would develop a line of attack, but I only did so after a lot of thought. Usually I did it based on close observation at PMQs. I never made it overly harsh. I always tried to make it telling. The aim was to get the non-politician nodding. I would wonder not what appealed to a Labour Party Conference at full throttle, but what would appeal to my old mates at the Bar, who wanted a reasonable case to be made; and who, if it were made, would rally.

“So I defined Major as weak; Hague as better at jokes than judgment; Howard as an opportunist; Cameron as a flip-flop, not knowing where he wanted to go. (The Tories did my work for me in undermining Iain Duncan Smith.) Expressed like that, these attacks seem flat, rather mundane almost, and not exactly inspiring – but that’s their appeal. Any one of those charges, if it comes to be believed, is actually fatal. Yes, it’s not like calling your opponent a liar, or a fraud, or a villain or a hypocrite, but the middle-ground floating voter kind of shrugs their shoulders at those claims. They don’t chime. They’re too over the top, too heavy, and they represent an insult, not an argument. Whereas the lesser charge, because it’s more accurate and precisely because it’s more low-key, can stick. And if it does, that’s that. Because in each case it means they’re not a good leader. So game over.”

There is a great temptation, over partygate, to go for what Blair calls “an insult, not an argument”. The Twitter mob will applaud Sir Keir to the rafters if he shouts insults at Johnson.

But in Live and let live Britain, people will think, maybe without saying anything, “that sounds a bit over the top”.

They may also have a degree of sympathy with those who had to take life-or-death decisions during the pandemic, and who did not have much time left over to think about the rights and wrongs of prosecco or birthday cake.

The pressure inside Downing Street during the pandemic was immense. Dr Carter Mecher, an American doctor who gave early warning to the White House and other parts of the US administration of how grave the crisis was likely to become, has pointed out that dealing with an emergency of this kind is like dealing with a bush fire.

“You cannot wait for the smoke to clear,” he has said, because “once you can see things clearly it’s already too late.”

You have to act before the fire is raging, which means you have to be prepared to be wrong. When hundreds of thousands of lives are at stake, that is a fearful responsibility.

While partygate dominated the news, reporters competed with each other to find the next piece of supposedly damning evidence, the next photograph of Downing Street staff with a bottle on a desk or whatever it might be.

And moralists competed with each other to say how unforgiveable this was.

We shall probably get some sort of repeat performance in the near future. Moralists will say all this is unforgiveable. Live and let live Britain will perhaps think they are getting things a bit out of proportion.