Colonel Gaddafi was accustomed to appear in public wearing enough insignia on his chest to cover a dining table.

Whatever else his medals were awarded for, it wasn't bravery. Ceausescu went to his death before a firing squad singing the Internationale. Saddam Hussein died shouting "Do you consider this bravery?"

But Gaddafi seems to have died the death of a coward, found in an outflow pipe, cringing. He shouted "Don't shoot, don't shoot", and according to one freedom fighter, "What have I done to you?" Considering the scale of Gaddafi's crimes, the freedom fighter might very well have been able to supply a precise and specific answer to the question. He was beaten, and, it seems, killed with a shot to the head. The images of a bloodied Gaddafi in his last momentsquickly went round the world.

What was the alternative? A long wait: a glass box in the Hague; interminable self-justifying speeches; a slow loss of interest by the media and public as the months dragged on; and a final, inevitable verdict which few could take much interest in any longer.

As theatre, the death of Gaddafi was surely unbeatable, and satisfied its audience richly. Like the Thane of Cawdor, nothing in his life became him like the leaving of it. He was revealed in his true nature by his last moments. Was it the right way to bring his brutal rule to a conclusion? What is the value of theatricality in these circumstances? For various reasons, it is in the interests of governments to demonstrate that its opponents behaved, or died like cowards. It discredits them in the eyes of those who might support them otherwise; it appears to demonstrate that there was no justice in their cause.

Bravery, of course, is no guarantee of rectitude, and if someone dies in a way which must have required bravery, there seems no reason to admire them for those reasons. Suicide bombers must be crazily brave people, but reasons of propriety require governments to describe them as "cowardly" in all circumstances.

The circumstances in which Osama bin Laden died, for instance, were initially stated by the US forces to show him in as cowardly a light as possible, and he was said to have used a woman to shield himself. Surely, it hardly matters whether Osama bin Laden died bravely or cowering behind his wives. Given the enormity of his deeds, no-one could think of him with admiration just because he met his death with bravery.

But the requirements of theatre demand that these people should show cowardice at the end, and in this, Gaddafi seems to have answered to requirements. There is no doubt of his total humiliation at the end.

Why the violent deaths of major public figures sometimes meet the imaginative requirements of the age with great exactness is an interesting, but rather puzzling question. The Duc de Berry's assassination at the Paris Opera in 1820 forms a very curious example. He was stabbed on the steps of the opera, embraced by his young wife. His beautiful widow later gave birth to a posthumous heir. The whole thing is astonishingly like the fantasies of a Victor Hugo, and the point is that sometimes everybody involved – the victim, the assassins, the audience, posterity – knows exactly how to behave. Such moments of theatricality are, in a way, more telling about the facts of the society than anything else. Perhaps, in acting out the fantasies of a society, they are more purgative, too.

The killing of Gaddafi shows exactly where Libya has got to, and, in the excitement of the moment, we might overlook how very ugly it is. In eight months of rising insurrection and protest, the opposition has failed to create a credible alternative structure of power.

There was no alternative to an angry crowd, dragging the dictator from his concrete pipe. Even Ceausescu, at Christmas 1989, was given a brief trial before being shot by firing squad. It was not much of a trial; it was, too, for the sake of the drama as much as anything; but there were officers, and an arraignment, and an event which afterwards could be examined by historians for its propriety and justice.

The theatricality of the Gaddafi execution had none of that. And yet it answered an evident, savage need in the Libyan people. They demanded not just that justice be done, but be seen to be done, immediately, on camera phone footage; they wanted to see with their own eyes that some fragment of the sufferings Gaddafi had visited on his subjects was returned to him. If they could, they would have put his head on a spike in the centre of Tripoli.

There is something pornographic about the enthusiasm for visible, immediate, physical punishment which is indifferent to justice. Some of the people who are watching the last minutes of Gaddafi with interest will also have seen – with what emotions I don't know – the samizdat films of judicial mutilations of minor criminals, beheadings of kidnapped Americans which circulate in the lower levels of the internet. Why they happen is almost irrelevant. What matters is the spectacle, freed from morality or rectitude.

It can't go on like that. Summary justice is no justice. Hardly anyone will mourn the death of Gaddafi, and plenty of people will say it saves a good deal of trouble and expense in the International Criminal Court. The mills of international law grind exceedingly small, and the proceedings hardly ever satisfy the enthusiasm for theatre which a dictator's end might seem to require.

A legal examination of atrocities can provide a national ceremony of purgation – think of the South African Truth and Reconciliation Commission, or the 7/7 inquiry here. But they can seem less satisfying than a powerless, cowardly gangster dragged from a sewage pipe, beaten and shot, like an episode of a brutal American TV drama.

As time goes on, the connections between our imaginative fantasies and these great events will become clearer; clearer, too, the way in which our duty to our civilisation tends to get left to one side in all the excitement.