Dill witnesses Mr. Gilmer cross examine Tom Robinson on the stand. Gilmer is not only hateful and sneering in his conduct and questions, his racism is blatant. At one point Gilmer says, "Are you being impudent to me, boy?" His question sounds very threatening. Tom is used to dealing with men like Mr. Gilmer and plays he role he is expected to play, deferring to Gilmer.
The ugliness and injustice of the whole scene makes Dill physically sick. He tries to explain his feelings to Scout: "It ain't right, somehow it ain't right to do'em [African-Americans] that way. Hasn't anybody got any business talkin' like that." Scout doesn't understand, but Mr. Dolphus Raymond, sitting nearby, does understand. He tells Dill, "You aren't thin-hided, it just makes you sick, doesn't it?"
Dill's unhappy family situation may have made him especially sympathetic to someone else's pain.
In Chapter 19, Mr. Gilmer cross-examines Tom Robinson and clearly reveals his prejudice by referring to Tom as "boy" and sneering at him. As was mentioned in the previous post, Dill becomes sick when he sees how Mr. Gilmer is disrespectfully speaking to Tom. In the middle of the cross-examination, Dill begins to cry. Scout does not get a chance to hear the rest of Tom's testimony because Jem makes her take Dill out of the courtroom. Initially, Scout does not understand why Dill began to cry and assumes that he is still upset about running away. When the two finally get outside of the courthouse, they sit down underneath a big oak tree, and Dill explains to Scout that Mr. Gilmer's hateful attitude towards Tom Robinson made him sick. Dill noticed that Mr. Gilmer spoke to the white witnesses differently and witnessing the blatant racism made his stomach hurt.
Dill feels sick to his stomach. He doesn't think anyone (regardless of race) should be treated that way.
Dill becomes sick to his stomach and wants to leave the room. Dill is honest and has a proper sense of justice. He believes, similar to Atticus, that one should not be judged based on their race. Dill feels absolutely sickened to see the real Maycomb and how others can brush over facts in order to prove their prejudices right.