> Man sitting in judgment on G-d is ridiculous.
Indeed. HaShem decides good and evil. If He commanded murder, we would murder.
It’s not murder fulfilling the laws of God, such as war or the death penalty for appropriate crimes. This situation with the Canaanites was a situation involving a war with nations that would seek to destroy you. These nations were also destructive to themselves with their practices ranging from human sacrifice to sibling incest.