Atticus is a very level-headed, unemotional man. He has the ability to see events and people from all angles, which makes him a very good attorney. After the trial, Mr. Ewell came up to him and spat in his face. Mr. Ewell was a tobacco chewer which means that all that tobacco juice went flying into his face. Even that didn't make him bitter. All he did was wipe his face off and later say, "I wish Bob Ewell wouldn't chew tobacco". Mr. Ewell threatened to kill him, and that frightened the children. They asked him to do something about it. Atticus just explained that they had to put themselves in Bob Ewell's shoes. "I destroyed his last shred of credibility at that trial" (pg 218). He explains to the children that ..."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." (pg 218)
When the children ask him about the trial, Atticus assures them that nothing would happen to Tom Robinson until a higher court reviewed his case, and that Tom had a good chance of going free. Atticus truely believed this. Therefore he had no reason to feel bitter. He goes on to tell the children that he feels that a person should not be sentenced to death on circumstantial evidence. He also tells the children,
"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 thoses are the facts of life." (pg 220)
He tells Jem and Scout that as they get older, they will see white men cheat black men every day of their lives. He tells them,
".....whenever a white man does that to a black man, no matter who he is, how rich he is, or how fine a family he comes from, that white man is trash." (pg 220)
There is no bitterness in this comment. It is just a statement of opinion. It has nothing to do with the trial --- it has to do with the general attitude of whites vs. blacks in the South.