A few did object to the treatment of Native Americans. Spanish missionary and historian Bartoleme de Las Casas (1474-1566) publicized the atrocities of the conquistadors.
He urged that Native Americans be treated humanely and that forced labor be abolished. In 1542, he succeeded in getting the New Laws passed, which aimed to end the encomienda system.
In fact, very little changed. Forced labor under other names, such as repartimiento, or assessment, kept Native Americans working under coercion.