The symbolism of the kite has already been discussed in The Kite Runner group. The rape was symbolic of complete and total humiliation of the spirit. It is total domination over another. The act also showed the evil in Asself's soul as one of his friends revealed that a homosexual rape was against Muslim teachings. That did not deter Assef.
Between the two boys, Amir and Hassan, the rape symbolized a rift that would never heal in Amir. Amir is haunted for years by his own cowardice and betrayal of his friend. His guilt causes him to drive Hassan and Ali to split with the family and move to a village that welcomes Hazaras. Amir never feels whole again until he can make right his act of cowardice, which he does in trying to save Hassan's son from Assef. The brutal, near fatal beating, at the hands of Assef assuages Amir's soul and releases his torment. His peace of mind will be achieved when he and his wife become a family to the brutalizes and orphaned Sohrab.