The Greens reckon that Peter Dutton is a sadist – that he positively enjoys inflicting cruelty on his defenceless victims.

But this is probably unfair to the potato-headed potentate. Dutton is certainly heartless, but his cruelty, while undoubtedly real, is more of an inevitable consequence of his demeanour than a deliberate agenda.

What the Home Affairs minister really enjoys is power – what George Orwell once described as the image of a boot stamping down on a human face. He exults in trampling his opponents, leaving them defeated and demoralised. He gets his kicks not so much from tormenting them, but from crushing them into impotent misery.

Thus the brutality of his treatment of the Sri Lankan asylum seekers from Biloela is almost incidental. What matters is his demonstration of supremacy – his ability to override all the normal standards of decent behaviour just because he can.

There is no conceivable rationality about his intransigence. The idea that allowing a single family to stay in the country where they have resided and worked hard for years, with the acceptance and affection of their Biloela neighbours and beyond, would destroy the entire fabric of border protection and unleash uncontrollable invading armadas is too silly to contemplate. Even for the likes of Barnaby Joyce and Alan Jones.

But not for our prime minister, who is in total thrall to his untouchable colleague. Scott Morrison’s response to the public outcry for common sense and compassion was an outright lie: “I know what happens when people think it’s okay to make an exception here or there. I remember the deaths. I remember those terrible images and I will never allow that to happen again.”

In fact ScoMo’s fanciful recollection has occurred not after an exception here or there but several, most notably last year’s medivac legislation. We were warned then of the onslaught of the people smugglers, but of course it never happened and there is no reason to believe giving succour to four Sri Lankans in regional Queensland would be any different.

And equally the message Morrison is so fearful about eluded the people smugglers when Dutton waived the rules to give a couple of au pairs visas to help out a rich mate. It should, for the record, be noted that this was not and is not evidence of inconsistency: the arbitrary glory of Dutton’s power extends to rewarding friends as well as punishing almost everyone else.

As does the dumping of the confected concerns over “on-water matters”, when it is convenient to orchestrate leaks to compliant media. And the midnight abduction to shift the Sri Lankans ever further from their friends and supporters, even the gratuitous nastiness of denying a birthday cake to the two-year-old, was less calculated viciousness than simple, systematic megalomania.

Entirely explicable, but hardly reassuring. As the Greeks used to say, the system of tyranny is only as good as the worst person who can become a tyrant, and Peter Dutton is well on track.