Answer:
Las Casas asserted that Spaniards are so cruel because he writes that Spanish Conquistadors have killed about fifteen million Native Americans.
Step-by-step explanation:
Bartolomé de Las Casas was one of the Spanish settlers on the land of New World. He was a priest by Profession. In his accounst about the new settling, he wrote about the cruelty incurred by Spaniards upon Natives.
He said that Spanish Conquistadors were cruel because they killed about fifteen million of Native. Spanish settlerrs were Christians, yet they murderered them for gold.
In his account he wrote that Spanish Conquistadors killed men, women, and children and those who survived were enslaved.
Their vices include multitude killings of Natives, enslavement of survivors, robbing, torturing, etc.