The first one was concerning Mr. Cunningham when the mob attacked the jail in hopes of hanging Tom Robinson. Scout talks them out of it, and, later, when Scout and Jem talk to Atticus about it, Atticus tells them,
" Mr. Cunningham's basically a good man.....he just has his blind spots along with the rest of us......you'll understand folks better when you're older. A mob's always made up of people, no matter what. Mr. Cunningham was part of a mob last night, but he was still a man." (pg 157)
This says that Mr. Cunningham was basically a good man, he just got involved in the emotions of a mob. That made him almost do an evil thing and kill an innocent man.
The second example is when Atticus is discussing juries with Jem. This occurs after the trial and after the verdict of guilty for Tom Robinson. Atticus tells Jem,
"Those are twelve reasonable men in everyday life, Tom's jury, but you saw something come between them and reason. You saw the same thing that night in front of the jail......There's something in our world that makes men lose their heads --- they couldn't be fair if they tried. In our courts, when it's a white man's word against a black man's, the white man always wins. They're ugly, but those are the facts of life." (pg 220)
This shows good in that the men are reasonable men, but evil in that they can't be fair and will convict Tom because he is black.
The pages I have given are from my edition of the book, but they should be in close proximity.