Oh yeah, I forgot about the Aztecs. Ritual sacrifice was practiced, as they themselves recorded. But even in your article, what actually took place in those Mezo American cultures is disputed.
Consider Spanish accounts of cannibalism near and around the Caribbean, as per your maps.
And consider cannibalism in Africa, which has been ongoing for millenia and continues to this day, a fact in which some Africans take great pride. To make a long argument short, the Spanish brought African slaves with them to the New World. Some of those slaves escaped and sought refuge among Native Americans.
Ba- da -boom. I think that's when you begin to read accounts of cannibalism by the supposed native population.
As for the OP, if that reading is authentic, and the incidental map illustrations are authentic, I would suggest that it was a lie perpetrated mainly by Christian leaders, especially by The Church, (but not by the Faith) to incite new comers and settlers to slaughter the Natives wherever they came across them in order to make way for Christianity, especially the power of its political organizations.