Comment by JPws_Prntr_Fngr

You use your time machine to travel back to the year 1350 and make contact with a Mesoamerican society that just loves to capture, torture, and execute their neighbors en masse, because doing this is a Good Thing. It pleases the gods or whatever. You think it's a Bad Thing though. You are now outnumbered 100,000 to 1. How do you prove to them that your moral code is the Universally True one, and not theirs?