It doesn't take us long to meet the kid, our protagonist in Blood Meridian. Cormac McCarthy actually orders us to look at the kid in the very first line of the book:
See the child. He is pale and thin, he wears a thin and ragged linen shirt. (1.1)
This is pretty cool because it's like McCarthy is an old-timey storyteller who wants us to close our eyes and picture this book's main character in all of his ragged clothing. No wonder he runs away from home. His family is dirt poor and his alcoholic dad is showing no signs of turning things around.
Once the kid leaves home, you'd think he was entering a world of singing birds and green meadows. But this ain't Bambi, this is the Wild West. Turns out that the world outside is home is ten times harsher than the world inside it. The kid finds himself stabbed and shot within his first few months on his own. His first boss is named Captain White and this dude ends up with his head floating inside a Mexican jar. When asked whether he feels sad about Captain White's death, the kid plays it cool:
He looked about the villagers and at the soldiers, their eyes all upon him, and he spat and wiped his mouth. He aint no kin to me, he said. (5.160)
The kid knows the score here. He's going to have to be tough if he's going to survive the American Southwest of 1850.
The kid knows the deal: the world is super harsh and you can't help other people without being punished for it. On more than one occasion, he's ordered to let a fellow cowboy suffer or die. But the kid never goes through with it. He always stepped out to help the wounded or the suffering. When Dick Shelby gets wounded, Glanton leaves orders to kill the guy and leave him behind. But as the book tells us:
The kid crossed to where the horse stood waiting and took the pistol and stuck it in his belt and hung the canteen over the saddlehorn and mounted up and looked back at the wounded man. Then he rode out. (15.64)
Little does the kid know that his actions have deadly consequences. He doesn't realize that Glanton and the judge have a supreme hatred for wounded or dying men, and it's not just because these men slow down the whole company. It's a matter of principle, too. Judge Holden and Glanton believe in a world where only the strong should survive and that's why they kill their wounded comrades instantly and without mercy.
So when someone like the judge sees "The kid put the pistol in his belt" (20.89) after letting a wounded friend go, he decides that this kid doesn't deserve to live in the Old West.
By the end of the book, Judge Holden is trying to kill the kid. After failing to do the job in the desert, the judge runs into the kid in a tavern ten years later and tries to explain why the kid disappointed him so badly. He explains:
You came forward, he said, to take part in a work. But you were a witness against yourself. You sat in judgment of your own deeds. (22.23)
In other words, the judge tells the kid that he (the kid) has been too soft. Deep down, the kid has judged himself harshly for hurting and killing people. The judge says there's no place for this kind of remorse or kindness in his world. And that's why the kid has to die. We're not sure we follow his reasoning, but we don't really have a choice but to go along with it.
We never really find out what happens to the kid in the outhouse with the judge. But before he heads outside, the kid runs into a prostitute, who he decides to confide in:
He told her that he was an American and that he was a long way from the country of his birth and that he had no family and that he had traveled much and seen many things and had been at war and endured hardships. (22.77)
Now that everything is said and done, the kid needs someone's sympathy. He needs someone to know he's had a tough life. He's tried to act like a brutal killer, but it's just not in him.