How is imagery used to convey Harper Lee's views on courage?

Courage is a major theme in To Kill A Mockingbird, expressed at various points through the behavior of many different characters. The childish courage of Scout in venturing into Mrs. Dubose's yard is contrasted with the moral courage of her father, Atticus Finch, who sets himself against the racist beliefs of an entire community in his defense of Tom Robinson. The language used to describe Atticus's courage makes it clear that his is not a militaristic strength and that Atticus "who hated guns and had never been to any wars, was the bravest man who ever lived" in the mind of his daughter, especially because he is armed with words and moral conscience, rather than weapons and bigotry. Atticus himself reiterates this idea: 
"I wanted you to see what real courage is, instead of getting the idea that courage is a man with a gun in his hand. It's when you know you're licked before you begin, but you begin anyway and see it through no matter what."
In Atticus's mind, then, black men like Tom Robinson have far more courage than those who would attack him, because he is starting from a losing position and yet tries to be courageous and moral anyway. As Atticus later vividly states, a white man who mistreats a black man "is trash," no matter who he is or where he comes from. 
Much of Lee's commentary about courage in this novel focuses on the idea of perception, particularly with regard to skin and race. Atticus tells his daughter that "most people" are indeed "real nice" "when you finally see them." It is impossible to understand another's point of view "until you climb inside his skin and walk around in it." This imagery is no accident: if a person wishes to be genuinely brave and morally upright, he must put himself inside the figurative skin of a black man, and imagine how difficult it must be to have courage when one is "licked before you begin".