The difference between the theory of the colonization of America, (which was) benevolent with the natives, and the practice, was large. In reality (fact), the Indians were slaves, and worked forced in the mines. During the first century of Spanish colonization of the New World there was a precipitous decline in the native population.
Bartolomé de Las Casas, a Dominican, was the first defender of the American natives, the first to denounce to the King and the world what was happening. Las Casas combated the abuses directly, through notices to the King, and through his writings. As bishop of Chiapas, in Mexico, he denied the sacraments to those who owned slaves.
He was a prolific author. His most famous work is the Very Brief Narration of the Destruction of the Indies. Directed to the King, it is not an impartial work. He accuses the Spaniards of systematic and prolonged brutality, equivalent to genocide.
According to Las Casas, the Indian is, by nature, virtuous and peaceful. His corruptions (the negative features found in him now) reflect the contact with Europe. This view of natives as superior to civilized people is new in Western history. In the eighteenth century it is called the myth of the "noble savage."
At the end of his life he went so far as (arrived at) to attack the legitimacy of the Spanish sovereignty in America. He enjoyed an enormous prestige and respect. His writings had much influence in Spanish legislation about the Indians. The slavery of the Indians was abolished.
Las Casas is even today a controversial figure. He is a hero of the Latin American left; a mistaken man, to many Spaniards. In effect, some positions of Las Casas were extreme. He failed to take into account, for example, the impact of the European diseases, introduced by the colonizers. Many Indians succumbed to them.
In order to cure the Indian exploitation, Las Casas proposed black slavery. The owners of haciendas imported black slaves to Cuba, Colombia, and other areas. Las Casas later repented for this suggestion.
The Spaniards also point out that Las Casas was not alone in his indigenist (pro-native) campaign. His extremism - typically Spanish, by the way - damaged his own cause. His works were very popular with Spain's many enemies. They contributed to the birth of what the Spaniards call "the black legend," the myth that Spain is an essentially evil country. This myth was popular in the countries - France and England - that were Spain's enemies.