When western media and the punditocracy fawn over an Arab political figure who is superficially liberal but fundamentally still quite a nasty piece of work, it’s never long before they are spectacularly disappointed. I call this Desert Rose syndrome, after a 2012 Vogue profile that chose to flatteringly portray Asma al-Assad as first lady of a “wildly democratic” household, in a country that was the “safest in the Middle East”, just as Bashar al-Assad began to intensify a crackdown against his own people.

The latest to provoke Desert Rose syndrome is Mohammed bin Salman, the crown prince and de facto head of government of Saudi Arabia. His western-friendly mien has won him many admirers, but they will have been pulled up short last week after the country cut all ties with Canada over a tweet.

Chrystia Freeland (@cafreeland) Very alarmed to learn that Samar Badawi, Raif Badawi’s sister, has been imprisoned in Saudi Arabia. Canada stands together with the Badawi family in this difficult time, and we continue to strongly call for the release of both Raif and Samar Badawi.

It wasn’t even a particularly dramatic tweet. Canada’s foreign minister, Chrystia Freeland, addressed the cases of two siblings, Raif Badawi, a blogger who has been imprisoned since 2012 for “insulting Islam through electronic channels”, and his sister, Samar Badawi, a women’s rights activist. Freeland said: “Very alarmed to learn that Samar Badawi, Raif Badawi’s sister, has been imprisoned in Saudi Arabia. Canada stands together with the Badawi family in this difficult time, and we continue to strongly call for the release of both Raif and Samar Badawi.” The Canadian foreign ministry followed up, calling for the release of “all peaceful #humanrights activists” held by Saudi Arabia.

Bizarrely, all hell broke loose. Saudi Arabia responded by expelling the Canadian ambassador, recalling its own, suspending Saudi Airways flights to Toronto, and ordering thousands of state-funded Saudi students at Canadian universities to leave their courses and continue them elsewhere. The Saudi foreign ministry stated via Twitter that “The Canadian position is an overt and blatant interference in the internal affairs of the Kingdom of #SaudiArabia and is in contravention of the most basic international norms and all the charters governing relations between States.” Further, it issued a warning: “Any further step from the Canadian side in that direction will be considered as acknowledgment of our right to interfere in the Canadian domestic affairs.”

The word overreaction doesn’t even begin to cover it. It was a tweet. And it’s Canada. This isn’t even new territory for Saudi Arabia: up until now there has been a broadly agreed-upon protocol governing how Saudi Arabia’s allies criticise the country (rarely, mildly and with no threat of action), and how Saudi Arabia reacts (rarely, mildly and with no threat of action). That is how the face-saving calculus works. But something has thrown it off kilter, and dangerously so.

The culprit is Bin Salman, a man who strives for status and is easily slighted. He is far from being the modernising prince that the New York Times, in its own badly timed Vogue moment, described as leading Saudi Arabia’s Arab spring “from the top down”. Every signature campaign Bin Salman has launched has ended up in a quagmire. The war in Yemen continues to claim civilian lives and taint Saudi Arabia’s international reputation. The blockade of Qatar, a petty and intense affair, is now more than a year old, a year in which the Qatari economy has continued to grow. By contrast, in June, it was reported Saudi Arabia had suffered a shock collapse in inward investment. Bin Salman even managed to botch his best hand, the end of the ban on women driving. The good PR evaporated when several women activists were arrested a few days before it took effect.

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And, of course, there is Trump. There is always Trump. Saudi Arabia’s increasingly erratic behaviour cannot be divorced from the broader suspension of diplomatic etiquette. Trump praises, encourages and is generally in thrall to dictators who scare their people and don’t have to deal with the limitations of democracy. (And, of course, he has picked his own fight with Canada.) Pugnaciousness and wars of fake news between erstwhile allies are now de rigueur. According to the Saudi press, Canada has no moral high ground from which to judge Saudi Arabia because it oppresses the good people of Quebec, and is holding the public figure Jordan Peterson as a prisoner of conscience. There are fewer and fewer adults in the room.

Saudi Arabia had always been indulged by the west for its ability to provide lucrative arms deals and other injections of cash. But now it seems to be acting with an enhanced sense of entitlement, demanding that even cosmetic expressions of concern about human rights cease. Under Mohammed bin Salman, the country has so far been involved in spats with Canada, Germany and Sweden, and embroiled itself in conflict with Yemen, Qatar and Lebanon. There is no “top-down” Arab spring here. Just a taste of what volatile princes, humoured by a gullible west, are capable of in a world where the old rules no longer apply.

• Nesrine Malik is a Guardian columnist