God was Good in the Old Testament.

In days long past, God told Joshua, the successor to Moses and commander of the Hebrews, to invade the Amorite territory (present-day Israel), to make no treaty with them, and to show them no mercy. The average, decent citizen was exempt, but like Nazism, the evil that the culture encouraged had to be stopped.

No Treaties but many exemptions

Treaties are not made with individuals. Treaties are made with groups allied for similar purposes. The average person was in no danger from God, but the culture in power encouraged evil such that it had irredeemably corrupted the minds of those who allied themselves with it. The society served evil. Three times the NIV reports that no treaty was to be made with the evil forces. On the other hand, God intended the unaligned, innocent individuals to be free from harm.

The culture, however, notoriously pursued wickedness for years. Early in the second millennium BCE, God told Abram that his family would expunge it. “In the fourth generation your descendants will come back here, for the sin of the Amorites has not yet reached its full measure.” (Genesis 15:16, NIV) By the time of the exodus, the culture’s evil course had reached the point of no return.

Amorite cruelty was stopped for then.

Nothing human beings do works out perfectly. No doubt the Amorite cruelty lived on in ways, but as with the Nazis, the mass movement was terminated. God did not do evil by fulfilling the role of perfect judge. I think the Bible and a long view of history demonstrate that evil is present, but God is good.