When does Atticus show courage in the book To Kill a Mockingbird?

After the death of Mrs. Dubose and Atticus's disclosure that she died free of any drugs by withdrawing from morphine, Atticus defines courage for his son: 

It's when you know you're licked before you begin but you begin anyway and you see it through no matter what. You rarely win, but sometimes you do (Ch.11).

This definition serves Atticus when he is asked by Judge Taylor to be the defense attorney for Tom Robinson, a black man who has been accused of the crime of rape. Before the trial begins, the town of Maycomb is filled with tense, hostile, and excited public feeling. On the day of the trial, there is a virtual parade of people from both the county and the town who cram the courtroom. Certainly, Atticus is aware that Tom Robinson has only the truth on his side. He is a black man accused of raping a white woman, Jim Crow laws are in existence, and the jury is made of twelve white men from the area. (True to his definition, Atticus "begins anyway.")
Even in spite of the fact that there is no medical evidence proving that any rape occurred, that Bob Ewell is a known reprobate, and that there are contradictions in the testimonies of the Ewells, Atticus does not count out any evidence in support of the defense. He very wisely disproves that Tom could have choked and struck Mayella: she testifies that she was injured on both sides of her neck and struck on the right side of her face—all indications that a left-handed man inflicted her injuries. Tom Robinson has a useless left arm, which was injured years ago.
In other instances, Atticus has the courage to follow his code of ethics, morals, and child-rearing. He holds to his convictions by not engaging in gossip about Boo Radley and by insisting that the children "leave that man alone." On the night of the pageant when his children are attacked, Atticus bravely accepts that Jem may have killed Bob Ewell. He refuses to lie to protect Jem from the consequences. (Later, Sheriff Tate informs Atticus that his son was not the one who killed Ewell; Boo Radley saved both Scout and Jem.)