Answer:
Mr. Underwood's editorial talks about how the people should be ashamed of themselves. It may as well have been a sin to kill cripples, and Tom Robinson's Death was "Senseless slaughter." He was an innocent man who did not deserve death.
Yeah, seventeen bullets is overkill, but at the time, racism was popular.
And don't worry, I memorized the book, I can assure you this answer is my own. TKAM is wonderful.