Good and evil has always been an issue for humanity. God was supposed to be good, Satan… evil. Of course, examining the bible made it difficult to judge which was which. With a million or deaths attributable to god and maybe 10 or so to satan, once could rightly be confused about the issue of good and evil.
For this post I am assuming as I believe… that god does not, did not, and will never exist. The concept of good and evil becomes the concept of moral and immoral. Rather than a good or evil god prompting evil behavior or good behavior, humans have the free will to choose what to do. (I also believe free will exists in the arena of choice)
This means that rather than god prompting the Crusades, people did. This means that witch burning, apostasy, blasphemy, are all in reality human concepts backed up by humans as far as punish or not punish. No god is making the decisions. Hitler made his decisions to burn up millions of Jews and wreak havoc on the world. The United States needlessly bombed Nagasaki and Hiroshima because of a man’s decision. Bombs, bullets, and tanks are not piloted by anyone but humans. The moral and immoral decisions that lead to good or bad outcomes are all the responsibility of human beings.
Slavery was a human decision. Select groups of humans were dehumanized so that they could be used and abused. That is the usual method to get society to accept the outrageous abuse of groups of humans, if not by race, by economic class, or education… or gender, as men are being denigrated today.
God and Satan are simply excuses today to do horrible violence to others. Even a baby in a crib is not safe as some religious groups insist a baby’s genitals be mutilated in accordance with some covenant with their imagined deity. Starting your life enduring a violent act is not conducive to peace.
The point of this post is this: If there is good or evil in the world it is housed in the minds of the men and women living in this world. It exists no where else. The concept simply is not something other creatures are capable of conceiving of… with the possible exception of some apes. (Discounting the possible existence of intelligent life elsewhere in the Universe… assuming that such life began as we did and evolved via evolution)