Whereas Atticus Finch is a scrupulous, loving, and gentle man who takes an active part in his children's upbringing, Bob Ewell is a dissipated reprobate whose conduct is reprehensible and even criminal; he is a neglectful, irresponsible parent who is even abusive physically and sexually toward his daughter Mayella, whom he intimidates into perjuring herself so that Tom Robinson will take the blame for Mayella's indiscretions.
Uneducated and absent from the home, Bob Ewell never contributes to the upbringing of his children; he spends his government check on liquor, and his children go hungry and unkempt. Certainly, he sets a poor example as he provides his children with no love or attention. On the other hand, Atticus dines every night with his family and sits and reads with Jem and Scout as they peruse the Mobile Register. When Scout comes home from her first day at school, Atticus counsels her that it is necessary to "get along with others." Further, he instructs her to "climb into his skin and walk around in it" in order to understand a person. In contrast, Bob Ewell acts upon that which will be advantageous to him, and Tom Robinson becomes the sacrificial victim to Ewell's efforts to "save face." When Bob Ewell is embarrassed in the courtroom by Atticus Finch, he vengefully spits in Atticus's face the next day after the trial as they are outside the courthouse. Atticus calmly wipes the spittle away and says nothing, displaying control and gentleman-like behavior.
While Bob Ewell hides behind his color in order to feel superior to others, Atticus Finch is ready to have Jem suffer the consequences of having stabbed Bob Ewell. His integrity is evinced many times in the novel--when he faces the mob outside the jail, when he defends Calpurnia to his sister, Alexandra, and when he walks away from Bob Ewell, ignoring his intended insult. And, it is this integrity which he imparts to Scout, who has learned to perceive things from the Radley porch and understand.
Two very different men, Bob Ewell is uneducated, self-serving, immoral, indigent, physically and sexually abusive, neglectful,irresponsible, and disrespectful; he is a terrible father. On the other hand, Atticus is a tender and loyal father, whose children repay him with equal fortitude and loyalty as they come to his aid before the jailhouse and in their front yard. He teaches his children to judge each person as an individual, and he imparts to them the real meaning of family. He insists that his children be respectful of others such as the dying Mrs. Dubose, and he tells them that blacks will not forget the injustice done to them. He disciplines his children without striking them, and he assists them in their growth as members of Maycomb's society. Above all, he leads his children to the deeper significance of his phrase that "to kill a mockingbird is a sin."