Atticus rarely has a bad word to say about anybody, but he has already told Scout that the Ewells had been "the disgrace of Maycomb for three generations." The present leader of the family, Bob Ewell does nothing to dispel Atticus' claim. Lewd, crude and socially unacceptable, Bob shows that he is out of place in any social setting.
All the little man on the witness stand had that made him any better than his nearest neighbors was, that if he scrubbed with lye soap in very hot water, his skin was white.
Bob referred to the prosecutor as "cap'n," making Scout feel sorry for her father's adversary. Bob soon had the courtroom in an uproar when he told the court that
"--I seen that black nigger yonder ruttin' on my Mayella."
As Scout explained,
With one phrase he had turned happy picnickers into a sulky, tense, murmuring crowd...
Bob showed that he was uneducated and uncouth, showing contempt for Atticus, the judge and the serious charges he and his daughter had made against Tom Robinson.