When more than 100,000 people have been killed, and thousands of others are in danger, the international community has a moral obligation to do what it can to limit the damage and reduce the suffering of survivors.
So why is it that the international community so rarely even tries? Oh yes, an unprecedented relief effort is taking place now in the areas of South Asia struck by last month's tsunami. That's laudable.
But when, in 1987-88, more than 100,000 people were killed in the Kurdish areas of Iraq, the international community turned a blind eye.
Those Kurdish victims were overcome not by waves of water but in some cases by waves of poison gas. Why should sympathy for those drowned on a beach be so much greater than for those choked in the streets of their village? More to the point, why should an act of God elicit more empathy than an act of man? The man in question, of course, was then-Iraqi dictator Saddam Hussein. Having slaughtered the Kurds with impunity, two years later he attempted to wipe Kuwait off the map
Only because President George H.W. Bush determined that such aggression "would not stand" were Saddam's troops forced out of Kuwait. But then, in 1991, Saddam began slaughtering Iraqi Shi'a, and he intentionally destroyed the environment inhabited by the Marsh Arabs, an ancient people of southern Iraq, leaving tens of thousands homeless.
And, again, the international community shrugged its shoulders.
World leaders, led by the United Nations, also shirked their moral duty in Rwanda in 1994, when more than 800,000 people were murdered.
And more recently, in the Sudanese region of Darfur, Arab Muslims have been slaughtering and raping African Muslims. As many as 80,000 people have been killed and at least 1 million have been driven from their homes. Hundreds of thousands remain in danger.
An international effort to stop the carnage and provide relief for the survivors is under way - but it pales in comparison with the effort being made on behalf of Indonesia, Sri Lanka and Thailand.
Politics is part of the explanation for this double standard. Governments and international organizations can do business with dictators like Saddam and with regimes such as that in Khartoum. Nobody can do business with a tsunami.
The media also contribute. Footage of bodies and mass graves along the Indian Ocean has been relatively easy to obtain and is being seen in the living rooms of millions of people around the world.
By contrast, pictures of the bodies and mass graves of Iraq were difficult for journalists to get and so few people saw such images on the evening news. (And Saddam made it clear what happens to journalists who displease him. In 1990, Farzad Bazoft, a British reporter, was executed for spying on Saddam's chemical weapons dumps.)
Beyond that, such intellectuals as Milton Viorst and Edward Said questioned whether atrocities such as the genocide of the Kurds even took place.
I've had personal experience with these phenomena. Twenty years ago, I was a young foreign correspondent in Africa when a famine broke out in Ethiopia. The old Africa hands told me the world would yawn. "Starving Africans," a world-weary colleague informed me, "simply are not news."
What's more, the dictator of Ethiopia, Mengistu Haile Mariam, denied that a serious tragedy was unfolding. Such allegations, he insisted, were imperialist slander directed against a Marxist nation. Most of the Western media were more than willing to give him the benefit of the doubt.
But a brave Ethiopian official by the name of Dawit Wolde Giorgis decided he could not turn his back on such suffering. He persuaded Mengistu to let him give the world a glimpse of Ethiopia's catastrophe.
The West could still be blamed, he argued, in particular the United States could be called stingy, reluctant to come to the aid of a country allied with the Soviet Union and Cuba. Several years later, after Dawit fled Ethiopia, he would tell me that he had known this was not true, but he also knew that his plan might save thousands of lives.
He was right: Film from the famine areas, taken by the late, great Mohammed Amin, a Nairobi-based Pakistani with a British passport, was soon on the BBC and then on America's televisions as well. Not long after there was an outpouring of sympathy. Bob Geldorf recorded "Do They Know It's Christmas?" Michael Jackson and friends recorded "We Are the World." A massive aid effort followed.
The world's greatest scientists don't know how to prevent natural disasters - tsunamis, earthquakes, volcanoes and hurricanes. Any fool knows how to stop unnatural disasters such as the mass murders of ethnic minorities by brutal dictators. We just don't seem to believe that both sets of victims are equally deserving of our intervention.