Underwood’s editorial is an example of the symbolism in comparing Tom Robinson to a mockingbird. The reader can infer that Underwood is not a racist.
Although the citizens of Maycomb think Mr. Underwood is showing off because he uses a colorful comparison, Mr. Underwood’s editorial has great symbolic value.
Mr. Underwood simply figured it was a sin to kill cripples, be they standing, sitting, or escaping. He likened Tom's death to the senseless slaughter of songbirds by hunters and children…(ch 25)
The reader has been introduced to the idea that it is a sin to kill a mockingbird because all they do is make beautiful music for us to enjoy. It is also a sin to kill a cripple, or someone who cannot defend himself. Mr. Underwood unknowingly echoes Atticus’s language.
Although Underwood focues on Tom Robinson's being a cripple, the fact is that his editorial also shows that he is not as racist as others in the town. The reader suspected this because he supported Atticus with the mob. By putting the editorial the way he did, he is being safe but still being brave in defending Tom.