What passages in Harper Lee's To Kill a Mockingbird tell us Tim Johnson, the mad dog, represents racism?

Inof 's
, one reason why we know Tim Johnson, the
rabid dog, symbolizes racism is the dog is shot to death by , one
who normally refuses to shoot anything because he values all of life too much. Since Atticus is
fighting racism by defending Tom Robinson , we know Atticus's
killing of Tim Johnson also symbolizes Atticus's fight...