I reject the philosophical notion, that there is no objective standard of "good" and "evil", thus that it is all subjective. Relativistic views of morality are quite fashionable these days. If there is not such thing as objective "good" or "evil" that means the moral judgment that oppression, slavery, racism, or genocide are wrong, is only relatively true or false to some particular standpoint. There were people and cultures who saw nothing wrong with slavery or oppressing and exploiting an entire population that was weaker than oneself. So in these cultures, slavery or oppressing people was not morally wrong or evil. When going by moral relativism then what goes on within a society should only be judged by the prevailing norms of that society. This is very problematic.