Anything that begins with a "myth" about peaceful or noble savages is already below historical standards. And your author is wrong regarding greater violence. The preserved bodies of prehistoric Europeans bear the same marks of violence. I've read about the studies on Native American skeletons and indications of violence. I've also studied European history. Some historians think that Europe was the most violent, war torn continent on earth for more than a thousand years, up to and including the 20th century.

Europe was at war continuously from the time the Byzantine empire attempted to reunite the western and eastern remnants of the Roman empire. Not to mention they were hell on their environment and had destroyed all their large predators, forests, and fouled the water with human and animal waste by the middle ages.   

Someone definitely needs to write "The Myth of the Superior European." As you might suspect, anything that follows such a title won't be focused on the positive.