In Defense of Moral Codes
Heuristics are good for decision-making, because we are bad at making decisions.
In fact, heuristics are better for decision-making than we think they are, because we are biased to think that we are better at decision-making than we actually are.
This, ultimately, is the value of moral codes. Having a systematic set of pre-defined rules and priorities into which you can input your decisions often has a better outcome than trying to do everything case by case.