I'm a pacifist and an atheist. I believe that murder, a taking away a person's only opportunity at existence, is immoral. I believe war is mass murder and as such one a great evil.
Still, war has been the greatest driver of technological advancement. Having to fight or die makes the species stronger and smarter. Wouldn't it be an even greater immorality to let humanity decline to morons living a soft life in a world of morons?
So I'll be out culling the herd. It's for the benefit of everyone. Are you strong enough and smart enough to stop me?