JUROR: #10: You're not gonna' tell me we're supposed to believe this kid, knowing what he is.
It's pretty early in the film that we realize Juror #10 is pretty darn racist. Comments like this one show us that he's willing to make a judgment about the kid's guilt based entirely on race.
JUROR #10: I've lived among them all my life. You can't believe a word they say. You know that. I mean, they're born liars.
When he sees that the rest of the room isn't with him, Juror #10 digs himself an even deeper hole by insisting that the defendant and all the other people of color like him are just born liars.
JUROR #9: Only an ignorant man can believe that.
When he can't take it anymore, Juror #9 (the old man) gets up and tells Juror #10 that he's ignorant for being so racist. He'd be happy to get into a much longer argument if it weren't for the people around him shouting him down.
JUROR #9: Certain things should be pointed out to this man.
Even after the other jurors have tried to calm him down, Juror #9 wants to give #10 a piece of his mind. After all, it's hard to get comfortable in a jury room when you know one of the jurors wants to convict the defendant just because of the defendant's race.
JUROR #10: Sure, there's some good things about 'em, too. I'm the first one to say that. I've known a couple who were OK, but that's the exception.
When he realizes that the other men aren't nearly as racist as he is, Juror #10 tries a classic racist backpedal, which is to say that some people of color are okay. #10 actually thinks this is a pretty enlightened thing to say, but all he's actually doing is showing the others how narrow-minded he is on the subject of race.
JUROR #10: Most of 'em, it's like they have no feelings! They can do anything!
In a final flurry of madness, Juror #10 starts shouting about how much he hates people of color. By this point, no one is listening to him, and he's talking out of sheer desperation.
JUROR #10: Listen to me. They're no good. There's not a one of 'em who's any good.
When he sees that no one agrees with his views on people of color, Juror #10 changes his mind about his earlier claim that some of them are okay. He goes right back to his original point, which is that no people of color are okay. And we can pretty safely assume that he feels this way about almost any race that isn't Caucasian.
JUROR #4: It's no secret that slums are breeding grounds for criminals.
Juror #4 may or may not be racist, but he definitely thinks that slums are bad places that tend to breed criminals. In this sense, he's more prejudiced against people from low social classes than he is against certain races. Yet it's also pretty clear that it's not only white people living in these neighborhoods.
JUROR #8: How come you believe the woman? She's one of "them" too, isn't she?
In a clever moment, Juror #8 uses Juror #10's racism against him. After all, #10 thinks that they should all believe the testimony of a non-white witness. But he also thinks that they should consider the defendant guilty because he's a person of color and can't be trusted. But if people of color can't be trusted, why does he want to believe the witness? Maybe the guy just wants to see someone go to the electric chair.
JUROR #10: I mean, what's happening in here? I speak my piece, and you… Listen to me.
By the end of the movie, Juror #10 has lost his right to speak to the jury room. It's clear that he has nothing to contribute to the general conversation except his racist rants. So it's time for him to sit down and shut up.