When Tom is being cross-examined by Mr. Gilmer he says, "I felt right sorry for her". Why was this a mistake? Why is it that "nobody liked Tom Robinson's answer"?

Mr. Gilmer presses him very hard, badgering him with questions. The mistake that Tom makes is when Mr. Gilmer pressurises him to explain why he always helped her out. Tom finally admits that he "felt right sorry for her." Note what happens as a result:

"Yes suh. I felt right sorry for her; she seemed to try more'n the rest of 'em-"

"You felt sorry for her, you felt sorry for her?" Mr. Gilmer seemed ready to rise to the ceiling.

The witness realized his mistake and shifted uncomfortably in the chair. But the damage was done. Below us, nobody liked Tom Robinson's answer. Mr. Gilmer paused a long time to let it sink in.

What was so bad about this is that Tom said this at a time when blacks were considered to be so much lower than whites. It was not correct for blacks to feel "sorry" for whites as that implied that blacks had it better than whites, which was something impossible in the Maycomb mindset at the time. Mr. Gilmer realises that Tom has said something that will not win him favour with the public or with the jury, and this is why he pauses for a long time. The comment Tom makes therefore relates to the racism in Maycomb society.