Are genocides an inevitable feature of human societies? If not, why do they continue to happen, long after we've all agreed "Never again"?

According to historian Daniel Jonah Goldhagen, it's because some political leaders see them as a way to achieve political goals.

"We must stop detaching mass elimination and its mass-murder variant from our understanding of politics. Eliminationist politics, like the politics of war, is a politics of purposive acts to achieve political outcomes, often of ulitmate ends and often of desired power redistribution." Daniel Jonah Goldhagen, Worse than War: Genocide, Eliminationism and the Ongoing Assault on Humanity

Contrary to much of the received wisdom about genocide, Goldhagen argues that it's never the result of irrational, frenzied bloodlust emerging from natural social tensions. In his view, genocides are planned and reasoned decisions: conscious political choices, with clear political ends. "Mass murder is a political act," he says, and any serious attempts to prevent it must take this into account. If genocide is indeed the rational, calculated action of political leaders, we need to make sure that leaders don't benefit from atrocities. "It's a political game....[and]...if people involved knew at the end of the day they'd be the losers, they would not play the game," says one of Goldhagen's interviewees.
 

You can read more about Daniel Jonah Goldhagen's views on genocide in this article from The New Republic:

http://www.tnr.com/article/world/ending-our-age-suffering

Let us know what you think? Do you agree with Goldhagen's description of mass killing? Is it always a calculated "top down" political action, or can genocide be sparked by natural societal tensions - ethnic, economic, religious, etc? What does that tell us about how to stop it from happening?