This almost reads like “that’s just your opinion man” with regard to human sacrifice. The Aztecs were hated by the groups they subjugated causing them to join with the Spanish against the Aztecs.
Society? Society cannot function for long without moral judgments. At least, it can't function well.
Caesar's wars were basically one long string of genocides and the Roman military principle "Murum Aries Attigit" meant that unless a besieged city capitulated before the Romans started attacking it, there would be no mercy to the captives.
It is like saying in a couple hundred years from now "For them, the gas chambers and crematoriums—the entire plan to purify humanity—evinced the Nazi's barbarism and justified laying waste to Germany in 1944."
Everything can be deconstructed, leaving nothing of meaning. “I ground him in the mill, down to subatomic particles, and there was not one atom of life! Not one particle of consciousness!”
Good and Evil do not exist, or so the argument goes, only arbitrary constructs. And yet. I look at the Aztecs; their worship of death, and I question.
I have been reading Team of Rivals, a deep dive book about Lincoln’s presidential cabinet during the civil war. It is amazing that many of the men write about how, after having personally witnessed slavery, they then vigorously oppose it. (Seward, for example, goes on a trip to the South for vacation and basically comes back hating slavery because it is so clearly wicked).
I imagine human sacrifice, death camps, gulags, they all evoke similar responses. ‘Societal good can only be reached through mass slaughter of the undesirable’ is the subtext. That should be repulsive to any with a functional moral core. The amount of suffering enacted by the Aztecs as they killed their neighbors children… I can’t imagine.
Note well: I am not endorsing the Nazis. I am merely pointing out a bizarre aspect of cultural relativism and associated movements.
Also note: They could make a case that the Spaniards were also in the "systematically conducting large-scale murder" category. But if that's the argument, then there's still a moral judgment to be made between civilizations.