It’s their culture. Read Bernal Diaz’ first hand account “The Conquest of New Spain”. If not for Cortez, the Mexicans would still be eating each other.
The King of spain sent Royal, explicit, and permanent orders to try to convert the savages, but forbad killing them except in self-defense.
In spite of not being 100% observed, dozens, if not hundreds of Monks died in its observation.
For those inclined to rely on documented history, rather than ignorant hyperbole, I could recommend a single book (out of dozens) that spells it out unambiguously.
The original journals and two-way correspondence still exist in the Spanish Royal archives.