I've got it from a book, which does have sources listed, but I don't have the book anymore. Its title was "Náufragos, traficantes e degredados", I don't think there's an English translation.

This wasn't because the Portuguese were nice, mind you. But the crown knew they did not have the population to control the vast overseas territories they intended to keep.

The Portuguese were about the first to sail South of the Equator, and that was fueled entirely on African slave trade into Europe. They weren't good guys by any measure. But they were pragmatic, and racism doesn't make any sense so it had to go.