Bob Ewell is despicable. Besides using his welfare check for his drinking habit and keeping the children from having the food they need, he exploits his daughter, Mayella, in order to elevate himself above the kind-hearted, humble Tom Robinson for the sole reason that Tom is black and Bob Ewell feels he must not let his family be perceived as lower than the lowest race in Maycomb. He perjures himself on the witness stand, attesting that Tom Robinson struck Mayella, but as Scout deduces, her father show[s] that "Mr. Ewell could have beaten up Mayella [himself]." Furthermore, he coerces his daughter to lie, as well. When, for instance, she is asked if Tom had beaten her on the face, she replies,
"No, I don't recollect if he hit me. I mean, yes I do, he hit me."
Ewell's indolence and indecency stand in such contrast with the decency of those such as Atticus Finch and Tom and Helen. Therefore, he attempts to pull them down to below his level by having condemnation fall upon them, either through a court ruling or by a public insult and spitting. He breaks into Judge Taylor's house and intimidates Helen; after the trial, he spits in the face of Atticus.
Ewell hates others because they are pure in mind, charitable, and forgiving; for, they remind him of what he lacks in character. He is so spiteful that he attacks the children of Atticus Finch in revenge for Atticus's interrogation of him in court. Clearly, Bob Ewell is the epitome of what is called "white trash" and deserves no compassion, no pity.