If God does not exist, then neither the holocaust nor the conquest in Canaan has the potential of being evil. This is because of the grounding problem of objective morality. If God does not exist, then objective moral values and duties do not exist. There simply is no foundation for objective morality. Not only do Christians believe this, but also many atheist philosophers, such as Jean Paul Sartre, Bertrand Russell, and Friedrich Nietzsche. If God does not exist, then nothing can be objectively evil. We are nothing but combinations of atoms and molecules that came together for no particular purpose, and will come apart again without any rhyme or reason to it. If God does not exist, then nothing that we do matters nor can any activity we engage in be truly evil. If God does not exist, then genocide is not evil because there is no such thing. In fact, our recognition that genocide, such as occurred in the holocaust, is evil provides us with good reason to believe that God exists.
We started by pointing out that the question of the conquest of Canaan is an internal question to Christianity. We have shown that the conquest has been erroneously labeled as a genocide. God had a righteous reason to judge the Canaanites, and it is entirely his prerogative to have done so. Even apart from the evil of the Canaanites, God cannot be accused of evil in any event that he calls back the life that he has given to people. Finally, we have seen that only if God exists is it even possible that things such as genocide can be evil. As it turns out, the very impulse that has caused the critic to challenge God’s existence over the conquest of Canaan is evidence for God’s that God does exist.
 Craig, William Lane. Reasonable Faith: Christian Truth and Apologetics. Wheaton, IL: Good News Publishers, 2008.