Sarty's dilemma is similar to that of the old South's; he is caught between defining his own identity and his fierce loyalties to clan.
When we first meet the 10 year-old Sarty we see him lying to the judge in the first trial. He has been taught to defend his father, no matter what. To go against one's clan is an unforgivable sin in the Snopes family. Sarty's father puts stubborn allegiance to clan above duty to God or even country. During the Civil War, Ab holds no real allegiances to either side; he steals horses from both the North and the South. In Sarty, he wants to continue the stubborn tradition of cut-throat immorality.
During the second barn burning incident at Major de Spain's, Sarty realizes he must rebel against his father's tyranny. His greatest misgiving is having to leave the rest of of family, to raise himself alone without his mother and sisters. In the end, he shows his burgeoning sense of morality and manhood as he leaves the clan forever.