In what way does Amir stand up to the general for the first time?

Amir and Soraya did not tell the Taheris the story of why exactly they were adopting Sohrab or how Amir had gotten injured. One day, General Taheri said, "People will ask. They will want to know why there is a Hazara boy living with our daughter. What do I tell them?" Amir, angered, told the general that Sohrab was the son of his illegitimate half-brother and told him never to call him a "Hazara boy" in front of him again.