This is a really good question. It starts the brain working overtime in seeking the connection between affairs of the heart and affairs of the state. I think that Hosseini's work illuminates how the fundamental flaw of targeting individuals is something that is a part of human nature and one that is reflective in society and government. Through Amir, Hosseini is compelling us to accept that we can recognize such a flaw in our own sensibility and seek to do right in order to "become good again" as the protagonist does. The reason behind why Amir needs to redeem himself is because he recognizes that he targeted Hassan. He might not have been as brutal in his targeting as Assef and his bullies were in that fateful afternoon in the alley, but he targeted someone who did not need to be targeted. Amir's targeting of Hassan is on a personal level, while that which is displayed by Assef and the Taliban is on a political and social level. The sins of exclusion are the same in both. It is for this reason why the conflict between Amir and Assef at the end of the novel is so significant in that it is a collision between forces of targeting on personal and on social levels. In recognition of this, Amir laughs as he becomes targeted by Assef, an understanding that he knows what Hassan endured. In this, Amir becomes "good again." The human flaw of exclusion and targeting individuals, focusing on isolation in order to substantiate one's own self is a flaw that Hosseini sees in both the individual human being and the social and political constructions that extend from this psyche.