Based on freuds theory of displacement why is amir being so cruel to hassan? How has hassan become a scapegoat?

Amir hates himself and has anger built up at his father. His failure to help Hassan is projected onto Hassan. Hurting Hassan is easier than only punishing himself. He projects all this angst on Hassan. Hassan cannot protect himself and readily takes on Amir's sins. Amir functions because Hassan takes on his guilt and anger.