Poor Prince Charles got into terrible trouble last week for stupidly saying something sensible. He was stitched up by the only witness to his perspicacious outburst, 78-year-old Marienne Ferguson. During a tour of the Canadian Museum of Immigration, in Halifax, Nova Scotia, she was telling him how her family had fled Poland in 1939 just as the Germans invaded, when the prince apparently said: "And now Putin is doing just about the same as Hitler." "I must say I agree with him," Ferguson later said, as she dobbed him in to the world's media, heralding headlines proclaiming that "Prince Charles says Putin is like Hitler!"

Illustration by David Foldvari.

I agree with him too – and he's not the first to say it. He's echoing the views of former US secretary of state Hillary Clinton, Canadian foreign minister John Baird, Czech senate speaker Milan Stech and German finance minister Wolfgang Schäuble. Vladimir Putin's current foreign policy towards Ukraine is uncannily similar to Hitler's behaviour towards Czechoslovakia and Poland in advance of his annexation of those countries in the 1930s. The prince's comparison is apt and chilling, and the fact that Putin shows no sign of wanting to exterminate an ethnic group, but is content merely to marginalise and harass a sexual orientation, does nothing to undermine it.

This private remark was meaningful, and therefore much more irritating to anti-monarchists and the Russian government than if the prince had said something daft, which he often does. But he's obviously going through a worried-about-climate-change rather than a convinced-of-the-benefits-of-homeopathy patch. And I felt sorry for him as the Russian foreign ministry spluttered in protest as if they don't know how horrible they really are, and the likes of Labour MP Mike Gapes slagged him off for talking at all. "If Prince Charles wants to make controversial statements on national or international issues," he said, "he should abdicate and stand for election."

Is that what Gapes thinks our elected representatives do – "make controversial statements"? Doesn't he mean "repeat crowd-pleasing platitudes"?

I don't think Charles was looking to be controversial in this case at all – he was trying to enter into conversation with a stranger in a more engaged way than just saying "Yes" and "Oh dear" and "Poland, you say? I once ate borscht!" I find it hard to blame him for that. But those who find it easy may be consoled by the thought that he isn't usually this insightful. This week's imprudent snippet of wisdom was only an accident – even a stopped clock tells the right time twice a day. The republicans and Russians might just get off his back if he made public some of the other historical comparisons he may have been toying with.

Damien Hirst is like Hitler

"Both absolutely terrible artists," the prince is often heard to opine. "And who's to say that if our age hadn't lavished absurd wealth and praise on Hirst, he wouldn't also have become crazed with hatred for an ethnic minority? We just can't know. He's hardly going to get into politics while he can still make a fortune selling dots, but I don't see why he should get much credit for that."

Eric Pickles is like Cardinal Wolsey

"I mean, do I have to paint you a picture? Huge and bloated with tiny, cruel eyes. And sadly, Pickles doesn't benefit from Wolsey's voluminous figure-forgiving ecclesiastical muu-muu. But you can see the link: the greed for favour, the greed for power, the greed. Building on the green belt – Hampton Court for the cardinal and endless Asdas for the secretary of state."

Melanie Chisholm is like Anne of Cleves

"Quite the Cleves of the Spice Girls, don't you think? Always the bridesmaid and all that. Although obviously A of C was actually a bride, albeit one whose marriage was then humiliatingly annulled. I don't know whether that's happened to Sporty but I wouldn't be entirely surprised to hear it had."

Charlie Chaplin is like Hitler

"I don't think it's just the moustache," says the prince. "There's something about him… something reminiscent… Actually, on reflection, I think it might be largely the moustache."

Max Clifford is like Genghis Khan

"Different times – different mores. Back in the 13th century you could lead a ravaging horde across thousands of miles of steppe, killing all who crossed your path and everyone thought you were the bee's knees. Whereas nowadays, no one drinks at lunchtime. If Khan was around today, he'd be arrested for crimes against humanity, not to mention pitiless horse cruelty. As it was, he died an emperor. It's just the same for Max Clifford and the 1970s: if someone had killed him 40 years ago, he'd have got away with it. Clifford, not the murderer. Or maybe both?"

Baroness Thatcher is like Joan of Arc

"Both strong women, possessed of an unshakeable righteous zeal, and both, ultimately, burnt by the English."

Nicholas Witchell is like Hitler

"Honestly, I just can't bear that man. I think I prefer Hitler, to be honest."

Russell Brand is like Jesus

"Look, I'm as Christian as the next man, who, as you can see, currently happens to be the Archbishop of Canterbury – but you can't deny there are aesthetic similarities. At times one gets to thinking and it's often occurred to me that I don't know whether I'd have particularly liked Jesus, if I'd met him, you know? I'm not proud of that. But I suspect I'd have thought he was a bit of a scruffy troublemaker. Gift of the gab and all that, but he'd make you feel uneasy. All the foot-washing – I'm not sure. Much easier nowadays, when the lord's representatives as often as not sport brogues like his lordship here. But I can absolutely imagine that Brand chap getting nailed up somewhere and making quite a hit of it."

Angela Merkel is like Hitler in a dress

"I think it's mainly because she's German and in charge of Germany – but that's a pretty good start. Except he was Austrian wasn't he? Like those cakes. Anyway, he's only Austrian in the same way that Poirot was Belgian – it's trivia really… Of course I accept there are political differences but I defy anyone to spend any time with the woman without thinking about Hitler pretty much constantly. I mean, I think about Hitler quite a lot anyway – him and architecture – but if I'm ever going to stop thinking about Hitler for a few minutes, it's very unlikely to be when she's in the room."