Why does Parvez hit Ali at the end of the story "My Son The Fanatic"?

Parvez hits his son Ali at the end of the short story “My Son the Fanatic”, because he is annoyed, even frustrated by his actions. Prior to this incident, Parvez and Bettina had picked up Ali from the streets in a poor part of town. Bettina is Parvez’s friend, to whom he has confided in about his son’s growing fanatical interest in Islam. When they pick up Ali, Bettina tries to talk to the boy compassionately, perhaps in an attempt to break through the shell he has built around himself. Her attempts are met by an insolent indifference. When she asks, “And how are you getting on in college? Are you working hard?” Ali’s response is, “Who are you to ask me those questions?” It is evident that Ali despises Bettina because she is a prostitute. After the difficult conversation she has with Ali, Bettina “throws herself out of the car” and runs away in spite of Parvez’s calls. Parvez is infuriated by his son’s actions and spends time “pouring one drink after another” when the two get home. When he finally gets to Ali’s room and finds him praying, he hits him repeatedly, even though he knows that he cannot reach the boy. I think that his anger is worsened by pent-up frustrations following Ali’s sudden fanatical religiosity.