The Aztecs are of particular interest because, compared to most other tribes, which were essentially stone age before interaction with Europeans, they had developed a pretty advanced civilization, but were absolutely merciless. There's an interesting reference page here. The stone age tribes saw human flesh as meat, and ate it. The Aztecs placed it in a religious context.
Of course, many pagan religions teach that eating portions of a vanquished enemy is a method of obtaining their courage. It's also a sign of ultimate dominance, and embeds fear in the surviving foes.
***Redford's movie Jeremiah Johnson cleaned up the reputation of the man. He was, during his day, known as Liver Eating Johnson. He hunted Crow Indians, killed them, and ate their livers. **
I read that years later Johnson admitted that he only passed the liver in front of his face to make it look like he took a bite out of it, but did not actually eat it.
I've read so many books on the old west I can't remember which book or magazine it was in.
Enjoyed your post, the link you provided doesn’t work - can you re-post it?