How does Underwood feel about Tom's death in To Kill a Mockingbird, and why did Lee choose to include Underwood's opinions about Tom's death?

Earlier
in the story, Braxton Bragg Underwood, editor of the local paper, silently stood watch overwhile
he was accosted by the group of Cunninghams bent on lynching Tom Robinson. He later called down
to Atticus from his second floor perch that he "had you covered all the time,
Atticus." When Atticus looked up, he saw Underwood with a double-barreled shotgun
leaning out his window. Atticus later told his sister,

"You know, it's funny about Braxton," said Atticus. "He despises
Negroes, won't have one near him."

Racist though he
may be, Underwood nevertheless found the...