They should have saved their knives and their aggression for the Spaniards, instead of using it on their own innocent citizens.
They were convinced they had it coming because they had done something to anger their gods. Just like the liberals of today are convinced we did something wrong to bring about 9-11. The proposed solutions are not dissimilar. The Incas sacraficed their own people to these false gods. The liberals propose to sacrafice western civilization to appease the false gods of radical Islam.
The Mesoamericans certainly had a natural right to repel such cruel, dishonorable and greedy aggressors as Pizzarro. The situation was not uniform, however, throughout the entire Spanish conquest. Conside Mexico: as Cortes passed through mountain towns and villages, many Indians told of cruel treatment by the Aztecs. These Indians were very willing to help the Spanish conquer Montezuma. Tlaxcalan allies, in fact, were the key to Cortes' victory. With all his faults, he was much more the "liberator" than was Pizzarro.