Today, thousands gathered in the Serbian capital Belgrade to pay their respects to Ratko Mladic, the head of the Bosnian Serb army, who was convicted of genocide and crimes against humanity by the International Criminal Tribunal for the former Yugoslavia (ICTY).

Anyone glorifying Mladic is approving mass murder of thousands of innocent people. What should we then make of the Serbian state that organised a funeral with state honours for him? Or of the Serbs from Serbia proper and the Bosnian Serbs who attended it?

Does the glorification, I have been asked, reflect the limits of international justice by showing that international law has failed to stop wars and whatever else can stick with the criminality of war?

First, the highly restricted ability of international justice to teach us anything has been proven by the wars started by the likes of Russian President Vladimir Putin and US President Donald Trump, to name but two.

With about three decades of international humanitarian law in action at international courts and tribunals from which to learn, they picked up nothing, it seems. Not even that their citizens mostly abhor wars and have no desire to be in them.

Putin’s war was never justified, but he has no qualms about feeding hundreds of thousands of his own people into killing machines to kill blameless Ukrainians. Trump’s wars are no different.

In comparison, the 1990s wars in the Western Balkans were comparatively less significant and historic, as Balkan conflicts usually are.

Lessons may yet come from the Russian, US, Israeli, Iranian and other major conflicts and wars.

Second, Mladic will, in all probability, be swiftly forgotten everywhere except in Serbia and Bosnia’s Republika Srpska. There are already university students from other parts of former Yugoslavia who do not recognise his name.

Were there legitimate war aims justifying in any way what he did? No. Was starving and shooting the people of Sarajevo justified? Never. Was killing 8,000 plus men and boys from Srebrenica justified? Of course not.

Is the lesson to be learnt from Mladic’s death and funeral how potentially good people can be made bad by bad political leaders and by experience in wars?

Their glorification of Mladic, however wicked, has to provide a universal lesson or no lesson at all. Perhaps it is important to remember from where Mladic emerged.

I first visited Yugoslavia as a schoolboy on a student exchange in 1963 and stayed – without knowing at the time – with a Serb family where the father worked for Aleksandar Rankovic, a famous Serb and communist politician considered to be the third most powerful man in Yugoslavia after President Josip Broz Tito.

The exchange family hosted me on the Croatian coast, in Plitvice near the famous lakes and in Belgrade where, with my schoolboy host, we waived flags for Tito and Soviet leader Nikita Khruschev, as they passed in a motorcade.

In 1971, I worked as a UK tour representative in Cavtat, Croatia and was an occasional bus guide for English-speaking tourists from Dubrovnik to Cetinje, the former royal capital of Montenegro.

At all times in all places and with all people, there was plenty of “brotherhood and unity” – the Yugoslav state slogan – to be seen and felt, regardless of whatever was bubbling under the surface.

In 1998, I found myself, as a UN employee, prosecuting Bosnian Croats and a Bosnian Serb for dreadful crimes against Bosnian Muslims and from 2002, prosecuting Slobodan Milosevic for all he did in the wars against Croats, Bosnian Croats, Bosnian Muslims and Kosovars.

“Brotherhood and unity” was no more. Political manoeuvring had removed it. Hating the others was now OK.

The lesson – always the same from wars – was that people can be turned by political and military leaders into killers. Sometimes it may seem justified – Ukrainians fighting Russians now, for example; other times not.

Was Mladic justified? A definite not. There was no justification for what he did in Sarajevo, Bosnia generally or Srebrenica in particular. He was a war criminal and should be recorded in history as one, in the way the UN ICTY judgments do.

As the former Yugoslavia started to break up, some Serbs and Bosnian Serbs were encouraged to believe that Serbia’s entitlement to hegemony of the Western Balkans could justify what Mladic was doing.

Hegemonic desire of leaders – Putin for Ukraine and the rest of the former USSR, Trump for resource-rich lands – justifies and excuses nothing. For Mladic’s mourners to justify his actions with the desire to control the Western Balkans or even simply to have all Serbs in a single state achieved by murderous ethnic cleansing of areas that had no Serb majority is as bad as killing someone in the street for a packet of sweets.

Mladic was extraordinarily bad. Are those who mourn him in public show today like him? They will in time, we can hope, realise that today’s event has no place in civilised society and that those taking part lose a claim to being civilised.

The views expressed in this article are the author’s own and do not necessarily reflect Al Jazeera’s editorial stance.