At the stat of the story you get a pretty clear picture of how Sarty's views are expressed in the authorial voice. This occurs when the father first confronts Sarty on whether he was just about to tell the officers on him. You can denote the shame that Sarty did feel for his father, the disgust for his tendency but, most importantly, you can detect the inner anger that he feels for having to be a moral slave to the wishes of a father from whom he is detaching psychologically and age-wisely:
"You were fixing to tell them. You would have told him." He didn't answer. His father struck him with the flat of his hand on the side of the head, hard but without heat, exactly as he had struck the two mules at the store, exactly as he would strike either of them with any stick in order to kill a horse fly, his voice still without heat or anger: "You're getting to be a man. You got to learn. You got to learn to stick to your own blood or you ain't going to have any blood to stick to you. Do you think either of them, any man there this morning would? Don't you know all they wanted was a chance to get at me because they knew I had them beat? Eh?" Later, twenty years later, he was to tell himself, "If I had said they wanted only truth, justice, he would have hit me again." But now he said nothing. He was not crying. He just stood there. "Answer me," his father said.
This is evidence that Sarty was already in full knowledge that what was becoming a tradition and habit in their family was wrong, immoral, illegal, and sinful. Notice how he regresses in this passage to explain this point, and how his authorial voice suffers an "in-between the lines" affliction for having wanted to let go of the suffering his father was causing others, and himself.