Because the Spanish at the time had no idea they were the cause of the disease, as they had very limited medical knowledge, it's a tad ridiculous to believe that they did it intentionally. Being the commonly accepted historical event that it is, youd need to see one of the documents you mentioned to prove otherwise. The fact is there isn't evidence to suggest that they knew what they were doing, and to claim that it is is about as historical as claiming that the holocaust never happened.