What the godless fans of John Lennon always seem to forget is that there is a well-known place where there are no countries, no religion, and nothing to kill or die for. It is a very peaceful place, at least when seen from this perspective. It is called "the grave". And it is no accident that so many people end up there every time a utopian - who is often an atheist, but doesn't have to be - puts himself in a position of power where he can attempt to build a New Man, a New Society, or a New World Order.
It's not atheism that causes this lethal utopianism. But the observable fact of the matter is that atheists are particularly susceptible to it.