In what way is Mr. Underwood's editorial in the Maycomb Tribune similar to Atticus' advice to Jem and Scout when they got their guns in To Kill A...

After Tom Robinson’s death, Mr. Underwood publishes an editorial. When Tom tried to escape, prison guards gunned him down, killing him instantly.

“Mr. Underwood didn't talk about miscarriages of justice, he was writing so children could understand. 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)

Earlier, Atticus had told the children that it was a sin to kill a mockingbird. Miss Maudie explained why: because they did nothing but make beautiful music for people and "sing their hearts out for us.” They did not damage crops or bother people in any way.

Mr. Underwood’s editorial condemns the guards for their excessive violence. It was not necessary to shoot Tom twelve times—it wasn't necessary to shoot Tom at all. Tom Robinson was like a mockingbird. All he did was live a decent, honest life and help someone in need, like a mockingbird who did nothing but sing. Just as Atticus explained to the children that it was a sin to kill an innocent mockingbird, Mr. Underwood explained to the town it was a sin to kill an innocent cripple.

Tom Robinson was unjustly accused of committing a violent crime. People decided he was guilty before the trial even started, and he ended up dying for an act that was not really even committed. His only ‘crime’ was being an African American man who felt sorry for a white girl and so tried to make her life a little easier.