Why does Columbus come to believe that the Native Americans are incredibly generous?

They ... brought us parrots and balls of cotton and spears and many other things, which they exchanged for the glass beads and hawks' bells. They willingly traded everything they owned... --Christopher Columbus

When Christopher Columbus reached the Bahamas in October of 1492, he believed that he had reached islands off the coast of India.  For this reason, he called the people that he met Indians.  The description above is directly from the journal of Columbus.  It is obvious that his impression of them is that they are generous because of the gifts that the Natives immediately brought him. Columbus realized through their generosity that he could enslave and exploit this population.  The population of the Taino was wiped off of the island within a generation of their generous meeting with Columbus.  Columbus forced the Taino to work in mines for the benefit of his new colony and the crown of Spain.