What does Atticus say about how Bob Ewell must feel?

In Chapter 23, Bob Ewell approaches Atticus outside of the post office and spits in his face. Bob then proceeds to curse at Atticus and tries to fight him. Atticus calmly tells Bob that he is too old to fight and walks away. After hearing about Bob's threats, Jem and Scout begin to worry about their father's safety. When Atticus notices that his children have been acting differently, he asks Jem and Scout about what's bothering them. Jem tells his father that he thinks Atticus should do something because Bob seems to mean what he says. Atticus tells Jem that Bob Ewell got all of the hate out of his system after Bob spat in his face. Atticus goes on to encourage Jem to view the situation from Bob's perspective. Atticus tells Jem that he destroyed all of Bob's credibility during the trial. He says,

"The man had to have some kind of comeback, his kind always does. So if spitting in my face and threatening me saved Mayella Ewell one extra beating, that's something I'll gladly take. He had to take it out on somebody and I'd rather it be me than that houseful of children out there" (Lee 134).

Atticus understands that he ruined Bob's reputation during the trial by describing how Bob Ewell beat his daughter for kissing Tom Robinson, then lied to cover it up. Atticus also realizes that Bob is extremely upset and seeks revenge. However, Atticus was wrong in assuming that Bob took out all of his anger when he spat in his face.