check out our:
"Which, gentlemen, we know is in itself a lie as black as Tom Robinson's skin, a lie I do not have to point out to you. You know the truth, and the truth is this: some Negroes lie, some Negroes are immoral, some Negro men are not to be trusted around women—black or white. But this is a truth that applies to the human race and to no particular race of men. There is not a person in this courtroom who has never told a lie, who has never done an immoral thing, and there is no man living who has never looked upon a woman without desire." (20.47-48)
On the one hand, Atticus is totally right: we need to judge people as individuals rather than by their race. No argument here. On the other hand, check out the way he calls the lie of racist stereotypes "as black as Tom Robinson's skin," once again associating evilness with blackness, although in a more figurative way.
"There's something in our world that makes men lose their heads—they couldn't be fair if they tried. In our courts, when it's a white man's word against a black man's, the white man always wins. They're ugly, but those are the facts of life. […]
"The one place where a man ought to get a square deal is in a courtroom, be he any color of the rainbow, but people have a way of carrying their resentments right into a jury box." (23.38-40)
According to Atticus, there's just something about race that makes white people crazy. His holding up Jem as an exception because of his youth suggests that whatever that X factor is, it's learned and not innate (and thus, perhaps can be changed through education?). He also acknowledges, in case it wasn't already obvious, that law isn't a pure realm free of the prejudices that plague everyday life—it's subject to the same problems as society at large. Usually Atticus is a voice of hope for change, but here he flatly says that racism is a "fact of life," suggesting that losing Tom's case severely dented his optimism concerning human nature—or else that, having sat through the case, Jem is ready to hear a truer, grimmer version of how the world works, instead of the sanitized Disney version.
[Atticus says] "As you grow older, you'll see white men cheat black men every day of your life, but let me tell you something and don't you forget it—whenever a white man does that to a black man, no matter who he is, how rich he is, or how fine a family he comes from, that white man is trash." Atticus was speaking so quietly his last word crashed on our ears. I looked up, and his face was vehement. "There's nothing more sickening to me than a low-grade white man who'll take advantage of a Negro's ignorance. Don't fool yourselves—it's all adding up and one of these days we're going to pay the bill for it. I hope it's not in you children's time." (23.40)
Here's a quick reminder that To Kill a Mockingbird wasn't written in the 1930s, when it takes place, but in the 1950s, in the middle of the sometimes violent civil rights movement: grown up Jem and Scout are paying for it.