Given the question: Question: "What were the letters sent to newspapers protesting?"  Context: "One of the first incidents of the book being challenged was in Hanover, Virginia, in 1966: a parent protested that the use of rape as a plot device was immoral. Johnson cites examples of letters to local newspapers, which ranged from amusement to fury; those letters expressing the most outrage, however, complained about Mayella Ewell's attraction to Tom Robinson over the depictions of rape. Upon learning the school administrators were holding hearings to decide the book's appropriateness for the classroom, Harper Lee sent $10 to The Richmond News Leader suggesting it to be used toward the enrollment of "the Hanover County School Board in any first grade of its choice". The National Education Association in 1968 placed the novel second on a list of books receiving the most complaints from private organizations—after Little Black Sambo."  Answer:
The answer is:
use of rape as a plot device