Another thing Dad likes to do is back me into a corner WRT morality and moral relativism- "Oh, but can you really believe that the act of rape doesn't have an inherent [wrongness]? Are you saying it was justified for [insert historical monster] to do [atrocity] because it would make him reproductively successful?"

I can't say I disagree with him on that. Evolutionary psychology isn't much help when it comes to evaluating moral claims.

I don't know the answer to "is there such a thing as inherent wrongness?" - it probably depends on what is meant by "inherent" and "is". But I'm much more confident in the idea that "God says so" is not a satisfactory answer to moral questions, even assuming the ludicrous scenario where 1) we know God exists and 2) we know what he says we should do. If God said we should gouge out the eyes of all children, does it become the right thing to do?