Earlier quoted context omitted.
The article is missing the forest for the trees. It assumes morality is relative. Morality is the product of the intersection of narrative and mythology on a group. Morality is the story a particular group (or civilization) is enacting: the program they're executing. All groups hold myths. Even atheist groups hold myths. They just think their myths are just "the world" or "reality" or "how we got here". Civilizations…
Civilizations that have (generally) destructive, punitive, insular, judging, self-righteous, and violent myths don't. This seems to be the opposite of history. Until recently, violence was one of the only ways for any civilization to persist. The advent of nuclear weapons changed that somewhat (but not if civilizations begin to use them). And most of the myths of a civilization seem to be a byproduct of their actions…
Being warlike enough to defend your society is one thing; being warlike enough to conquer neighbors who hate you, or to throw away lives and wealth in pursuit of glory, is something else. Sparta, Assyria, and the Aztec Empire didn't turn out so well, after all...