Final answer:
The author included information about the 39 Spaniards killed by the Tainos to highlight the brutality of the Spanish colonization and promote the 'black legend' against Spain.
Step-by-step explanation:
The MOST LIKELY reason the author included information about the 39 Spaniards killed by the Tainos is to highlight the violent behavior of the Spaniards and their disregard for the lives of the indigenous people they encountered.
By including this information, the author is emphasizing the brutality of the Spanish colonization and the negative consequences it had on the native populations.
This information also contributes to the promotion of the 'black legend' against Spain, which portrayed the Spanish as ruthless conquerors and justified the colonization efforts of Spain's imperial rivals, such as England.