I loved the first Pirates of the Caribbean movie. I loved it because it was a great and fun story. But the compass -- the compass really was an intriguing thing. The compass points towards whatever a person desires the most.
That is exactly how our moral compasses work. Whatever our hearts desire most is what we steer by. If we have ever watched ourselves justify something that we know (objectively) is harmful, watch how skillfully our arguments change so we are again pointing to our own "true north."
(I know, I know, the Pirates story was full of morally questionable characters doing morally questionable things. But anyone getting their sense of morality from Disney pirate flicks has far larger problems than whether Disney is willing to turn their rogues into role-models. They did get one important thing right: the joy of living.)