Question about the nature of morality

Topic Suggestion/Request:
Question about the nature of morality

Reasoning:

I was talking to a pastor about slavery/genocide (basically racism by proxy) and it became clear to me that one of us had a fundamental misunderstanding of the nature of morality. My understanding was basically that something was either inherently good or inherently evil, and the fact that God cannot/won’t sin basically meant that he could/would not do something that was inherently evil. His belief seemed to be that nothing was really inherently good or evil, and that anything God does is basically automatically “cleansed” for Him and made to be “not evil” but that it doesn’t make it “not evil” for us. Are you able to explain the proper understanding of how this actually functions?