No, the authors seem to suggest, "be as good as the average person can be":

"He excludes from the scope of ethical obligation not just the literally impossible, but also anything that is merely beyond the abilities of the normal person. Ethics cannot tell us to do what would require the impartiality of saints or the foresight of seers."

Superman is not ethically required to save the world from the giant meteor because the average man could not. I, as a professional programmer, am not required to make ethical choices when writing software because the average person cannot write code at all.