If one makes a human moral claim then it applies to all humans at all times simply because the human being is fundamentally the same regardless of culture, nation or costume etc. So if I claim that murder is moral then I accept that it is good for me to be murdered. However, the very definition of murder is to not want to be killed. If I want someone to kill me then it's not murder. This is where it fails. I can't want to be murdered and not want to be killed simultaneously. If I make the claim that murder is immoral then it logically and consistently works and the same applies to rape and theft.