Amir struggled daily with the concept of Hassan being his "Hazara servant" versus Hassan as his "friend."
"Amir follows some noises to an alley off the bazaar where, undetected himself, he discovers a horrific scene: Assef, Kamal, and Wali threaten to take the kite from Hassan; Hassan, unable to fight them off, is raped by Assef while Assef's friends hold him down. Rather than step in and fight Hassan's attackers, Amir freezes, remains hidden, and eventually runs away in fear. "
Amir's fear of being hurt and raped himself cause him to stay hidden, his fear of his father's disapproval cause him to keep from telling the truth. He did not want his father to think him more of a coward than he already did, so Amir said nothing.
Would things have been different if he had done the right thing and told his father what happened? Absolutely things would have been different. Had Amir spoken up about what happened he would not have lived his life with the guilt and fear that followed him throughout his life. He would not have gotten Hassan in more trouble later, and he would not have turned his back on this friend. Anytime we choose to lie instead of tell the truth there are going to be consequences. Any time we choose to tell the truth instead of hide in the lie of omission, there will be life changing results.