Morals are whatever society accepts as moral. You cannot apply the morals of one society to another. It is understandable how Ruth Benedict could come to such a conclusion after having studied various cultures. The differences can be incredibly wide, but she ignores the deep cross cultural similarities.
Moreover, she also ignores several additional problems. Number one is how complete must acceptance of a moral position be before it can be regarded as entirely correct for a given culture? If 1% of the population disagrees, does that make the moral position questionable? What about 12%? What about 34%? To put it another way can 50 million Frenchmen be wrong?
I know that needs an explanation. This was the title of a song in a musical comedy. Basically, it was comparing the openness of France in the 1920s with prohibition and censorship in United States. Was it right for us to censor literature and prohibit alcohol when 50 million Frenchmen thought both were just fine? In the context of our discussion, was French culture different from American culture? How different was it? Could something be right in France and wrong in America? Good questions.
The second problem is a problem of legality. Once again I will go back to the most extreme case I can think of and that's the Natzis. After World War II, one of the roving bands of mass murderers called einsatzgruppen were arrested and tried. Their defense was that they had been raised in Nazi Germany. As children they have been forced to join the Hitler Youth. Both there and in school they were taught the Jews were not human but instead were hideous monsters determined to destroy humanity. In other words, killing them was self-defense. Their legal stance was, since we thought we were committing an act of self-defense we should be acquitted on the grounds of having acted in self-defense. Their argument was rejected and they were convicted...unlike George Zimmerman.
According to Ruth Benedict's position, the Nazis actually had a very good case. And if we could ask her this question, how would she respond? I doubt very much she would justify these atrocities simply because the culture that existed at that time in occupied Europe considered these acts to be moral. Or perhaps she might. In which case, I think most people would agree that she was in the wrong.
My final point is that she ignores the simple reality that we are social animals. That is to say, we evolved from lesser species and in the process developed ways to relate to each other and live in groups. That being so, our morals must also have evolved. Recall the cases of the capuchin monkeys and the chimpanzees in labs we discussed esrlier. Animals in the wild, especially higher primates, have been observed to display what can only reasonably described as moral behavior.
Consider a new case, the vampire bat. Vampire bats live by biting large mammals and lapping up the blood that wells up into the bite mark. A vampire bat that has not successfully hunted often begs a bloodmeal from a fellow bat. This is almost always granted. People who misunderstand evolution assume that if evolution were real, all bats would become beggars and the entire colony would starve since no one would hunt. But evolution has developed an excellent answer, morality. A bat who continually begs meals from others and does not reciprocate by feeding his fellows when they are hungry is excluded from the group. No one will share with him again. He is forced to hunt or starve.
This demonstrates the evolutionary value of morality.
I would agree that what is moral for a human may not be moral for a frog. However, human morality has evolved for our entire species. It is not absolute, but it is not optional either.