We know that different societies have different moral codes. Is there any reason to think that the moral codes of modern, educated, industrialized societies are better than more traditional ones?
Of course, it is impossible to use moral codes themselves as such reasons. That would be question-begging.
If the observable variation in moral codes is not a brute fact but can be explained in terms of distorting factors impinging on a shared moral basis, it is possible to imagine that there one code could be subject to fewer distorting factors than another. Such a code would probably be a better code.
So, we would have reason to think that the code of an “advanced” society could be better if there were fewer distorting factors impinging on it.
Two distorting factors are ignorance and error concerning material facts. “Advanced” societies know more than “primitive” ones. They have ways of eliminating mistakes. Hence, it is likely that their moral codes are better.
If my moral theory is peculiarly modern in declaring that we should neither damage nor destroy others but preserve them damage or destruction, and that all are fundamentally equal, then that fact is in its favour.