Atticus tolerates Mrs. Dubose's insults and cruelty by being understanding of the fact that she suffers from a morphine addiction. Whenever he sees her, Atticus is always gallant and polite.

After he meets the children on his way home from work in the evenings, they approach Mrs. Dubose's house. Atticus sweeps off his hat and greets her with chivalry, "Good evening, Mrs. Dubose! You look like a picture this evening."

Although he is aware of Mrs. Dubose's condition and the circumstances surrounding it, Atticus merely tells the children that this venerable neighbor is aged and ill. He encourages them to hold their heads high and be polite. No matter what she says, he instructs Jem and Scout, they should not allow anything to arouse their anger. Nevertheless, Atticus finds Jem angry many an evening when the children meet him.

"Easy does it, son.... She's an old lady and she's ill. You just hold your head high and be a gentleman. Whatever she says to you, it's your job not to let her make you mad."

Unfortunately, Jem does become angry, and he retaliates against Mrs. Dubose by destroying the blooms on her camellia bushes. After his act of retaliation, Atticus makes Jem read to Mrs. Dubose. It is then that Jem and Scout learn of Mrs. Dubose's condition, and Jem is sorry for his actions.

Mrs. Dubose is a neighbor who lives on the same street as the Finch family. When Jem and Scout walk by her house, Mrs. Dubose shouts insults from her front porch. One day, Jem goes home angry after a series of insults from Mrs. Dubose. His father tells Jem to calm down and consider Mrs. Dubose.

She's an old lady and she's ill. You just hold your head high and be a gentleman. Whatever she says to you, it's your job not to let her make you mad (Chapter 11).

When Scout and Jem walk with their father, he greets Mrs. Dubose as they pass her house. He takes off his hat and greets her with a compliment.  

After Jem chops up Mrs. Dubose's camellias with Scout's baton, Atticus admonishes him. He tells his son that "to do something like this to a sick old lady is inexcusable." He recommends Jem apologize to her.

Atticus shows empathy toward Mrs. Dubose. She is a sick woman with a morphine addiction. Though she says unkind things about him, he shows her compassion. He also wants his children to show her compassion. Atticus tolerates Mrs. Dubose and her cantankerous ways because he sees her as a human being in need of compassion instead of a cranky old lady. He ignores the unkind things she says to him. He always treats her with respect and friendliness, no matter what she says.