Scout states that Atticus was feeble (weak) at the start of the chapter. But later in chapter 10, both Jem and Scout change their minds about Atticus.
Later in chapter 10, Atticus shoots the dangerous dog that has rabies. He was able to shoot the dog with just one shot, and without his glasses. Scout and Jem learned that Atticus was known as the best shot in Maycomb. This made Scout and Jem respect Atticus much more, and realize that Atticus has many talents.
It is a sin to kill a mockingbird for this reason.
Mockingbirds do not harm to crops or people. Mockingbirds just sing their hearts out. So, they represent innocence.
Heck Tate, the sheriff of Maycomb, does not want to shoot the sick dog for this reason.
Heck Tate knows that Atticus is the best shooter in all of Maycomb county.
Atticus cuts off Heck Tate when he begins to tell Jem and Scout what a good shooter Atticus is.
Atticus does this because he does not want his kids to look up to him for being a good shooter. Atticus wants his kids to respect him for being a wise good man. He also does not like to brag about his talents.
Scout wants to brag to her friends about how Atticus shot the rabid dog. But Jem tells her that they should not do that.
Jem is a few years older than Scout, and is learning to be man (gentleman) from Atticus’ fine example. Jem wants to follow Atticus’ directions and not brag about the shot. Whereas, Scout is younger and has not yet reached the same level of maturity in this situation.