AFTER decades of witnessing how war can turn ordinary people into demons, I'd like to think I was pretty unshockable.

Looking back on a litany of horrors there are many that come to mind. There was the time during the Haiti revolution in 2004 when I found myself wading ankle-deep through human blood in a tumbledown morgue filled with massacred civilians.

It was the same in another charnel house in Tripoli filled with the charred remains of tortured victims of the Gaddafi regime. Then there was that terrible day in the eastern Congolese town of Goma when all I could do was look on helpless, unable to intervene as rampaging soldiers raped women in the street.

You might think that years of seeing such things might inure a person from the shock of the grisly act depicted in video pictures from Syria this week.

I'm talking about footage said to show a Syrian rebel commander called Abu Sakkar, cutting out and eating the heart of a dead government soldier. While the veracity of such pictures is sometimes questionable, in this instance they seem genuine given that Abu Sakkar has been identified by both US-based Human Right Watch and journalists who have met him.

Watching the video I was shocked. Why would any human being not be?

Far from making it easier to be detached, years of exposure to such atrocities only makes me more appalled. It is only when all sense of reason and compassion is lost that such barbarism breeds like a malignant disease. Most war reporters I know, far from being uncaring, are profoundly moved or upset by the things they see. Only by being so can they authentically tell in words or pictures the truly disgusting nature of war. Battlefields have always been harsh places.

But so many of war's worst atrocities take place not on battlefields but in the terrible sideshows that surround them where civilians bear the brunt. If men who call themselves soldiers can eat the hearts of their enemy combatants, what are they then capable of towards those innocents who cross their path?

War is history's most repugnant habit and will always be so. If Abu Sakkar is guilty of this atrocity we must remember that he is only one man. On Syria's front lines and elsewhere there are others like him that are equally vicious.

It's often been said that in a civil war like Syria's the firing line is invisible, and in reality it passes through the hearts of men.

This may be so, but if war brings out the worst in people it also reveals the best of human qualities. Compassion, love, selflessness and an enduring sense of justice also inhabit the war zones of the world.

And speaking of justice, if the actions of Abu Sakkar remind us of one thing, it is the importance of holding to account those guilty of committing war crimes, no matter how long it takes. We may not be able to stem the bloodletting in Syria right now but in its wake it is within our capacity to ensure that national trials, detailed human rights documentation, truth-telling and reparations all have their place. Where appropriate, too, the International Criminal Court (ICC) must be given the necessary jurisdiction to hold to account those guilty of war crimes. We owe Syria's victims that much at least.