Justin Taylor does a good and succinct job of answering this question that some nonbelievers may throw at Christians. And our young people may have this question as well.

When God commanded wiping out the nations of Canaan, doesn’t that make him a moral monster?

Here are his points:

1. As the maker of all things and the ruler of all people, God has absolute rights of ownership over all people and places.
2. God is not only the ultimate maker, ruler, and owner, but he is just and righteous in all that he does.
3. All of us deserve God’s justice; none of us deserve God’s mercy.
4. The Canaanites were enemies of God who deserved to be punished.
5. God’s actions were not an example of ethnic cleansing.
6. Why was it necessary to remove the Canaanites from the land?
7. The destruction of the Canaanites is a picture of the final judgment.

He elaborates on each one.

This might be a good question to quiz our older children.  “Some people say that God’s wiping out of the nations in the OT make him unjust and a moral monster.  What would you say?”