You’d think that they found the skeleton and remains of Jesus who had not risen from the dead. First there was disbelief then anger.
Back to your point, it is certainly understandable that claims of cannibalism got the white Europeans excited, since civilized persons had already rejected cannibalism for quite some time. Remember Idi Amin? Heh heh heh! That got em going.
Cannibalism was practiced extensively by the Aztecs starting as a part of state policy shortly before the arrival of Cortez. There was a “prime minister” who declared let us make them [surrounding tribes like the Tlaxcallans] our bread basket. They engaged in “flowery wars” and brought home thousands of captives who then had their beating heart cut out of their chest and then the bodies given to the people as a sort of communion. There was a definite shortage of animal protein in the diet of the people so this made a difference nutritionally. The religious sanction may have reduced any potential squemishness on the part of the populace. At any rate this is why Cortez with such a small number of soldiers was able to conquer the Aztecs. He had 100,000 angry, willing Tlaxcallan and other allies to help with the fighting.
A few decades after Cortez’s conquest there were several terrible plagues that decimated the Mexican population.
On a separate note, an officer of Pizarro’s [I think the name was Carvajal] ended up having to boat down the Amazon from the Andes to the Atlantic. He recorded a very well settled Amazon shoreline with tens of thousands of Indians. Apparently, they were pretty much gone when later explorations were made. The Indians treated these strangers reasonably well, and probably were infected with the Spaniards’ diseases by way of return.
I noted the reference to Yaws being identified in Indian skeletons from more than 1,000 years earlier. Perhaps there was some travel between or from Africa and the Americas.
I did some research on the claims of Anasazi cannibalism — my work was between the time when the coprolite was found and when the myoglobin test results were released — proving cannibalism to a degree of certainty that would get a conviction in a court of law.
Most anthropologists today accept that cannibalism has occurred on every continent at one time or another. They stress that this one proven incident does not prove a pattern of behavior, any more than an excavation of Auschwitz a thousand years from now would summarize 20th century Europe.