Atticus comforts Helen Robinson, but does not let Bob Ewells threats get to him.
Atticus is saddened by Tom Robinson’s death, by he stays out of the spotlight. He knows that he did the best he could. He does not allow Bob Ewell to get to him. He is aware that in the days following the trial and Tom Robinson’s death, Bob Ewell claims that he is going to get revenge.
Maycomb had lost no time in getting Mr. Ewell's views on Tom's demise … that Mr. Ewell said it made one down and about two more to go. (Ch. 25)
In fact, later on when Ewell threatens Atticus and spits in his face, Atticus does nothing. All he says of the incident is that he wishes Ewell did not chew tobacco, because it made his spitting in Atticus’s face more gross! This demonstrates Atticus’s diplomacy and aplomb. He remains always calm, cool, and collected while Bob Ewell goes further and further off the deep end.
Bob Ewell is embarrassed. He feels that Atticus made a fool out of him in court by proving that Mayella was not raped by Tom Robinson. Atticus defended Tom, a black man, and that is simply not done. He is a race traitor, in Ewell’s mind. So Ewell wants revenge. He tells anyone and everyone who will listen. Atticus actually sympathizes with the man.
I destroyed his last shred of credibility at that trial, if he had any to begin with. The man had to have some kind of comeback, his kind always does. (Ch. 23)
Atticus thinks that Bob Ewell is a simple, sad man who is drinking himself into oblivion. Unfortunately, while this is somewhat true, Ewell has just enough gumption to act on his desire for revenge. He is too cowardly and weak to target Atticus again, so he targets his children. He does more than spit. He goes after them with a knife. Fortunately, Arthur “Boo” Radley is there to save them. If he hadn’t been, the children might have been injured or killed, and Bob Ewell would have proven more than harmless.