Answer:
Dill is upset because he does not like the way that Mr. Gilmer talk to Tom Robinson.
Step-by-step explanation:
For example when Tom says that he felt pity for her, that made Mr. Gilmer angry as he was a black man, he had no place to feel pity for her, as she was a white woman. Also, that Mr. Gilmer is still adjusting that because Tom was black he was surely that he raped Mayella and keep on keeping the fact and keep on saying that the gave him the chance to raped her