rules do not, have apparently never, prevented rape, murder, pillaging (lol... pillaging?!). it just makes those things only be ok for the rule makers, or sometimes for those working for the rule makers.
edit: re "whatever that means" and deferring -- i'm sorry that i'm not being clear. it is exactly what you're acknowledging in both those phrases--acknowledging that there is no ultimate moral certainty, no universal good that all people agree to (much less act on)--that is in contradiction with some of your comments (things like "humans are generally reasonable").
(i edited this after FA's comment below, so they might not be giving the second part a thumb's up! ;) )