Sepulveda argues that the Europeans (particularly the Spaniards) were far superior in intellect, morals, and technology in comparison to the Native Americans. Sepulveda outlines these arguments in his famous speech called "Sepulveda Belittles the Indians. " In this speech, he talks about Native Americans as a barbaric people who do not possess creativity and were only able to develop complex societies out of necessity. Along with this, he goes on to discuss how these individuals are "slaves" to their own King and have almost no independent thought.
All of this information is meant to support this argument. His argument is based around the idea that the Spanish should continue to conquer and taking over Native American territories, as they will be able to pass on their civilized and superior beliefs to these people.