The Kite Runner

I am currently reading The Kite Runner by Khaled Hosseini, it is about a young boy, Amir, growing up in Afghanistan during the 1960's. I noticed while reading that there is a social class in Afghanistan and its divided between the Sunni and Shi'a muslims. The Sunni muslims also called Pashtuns are the richer, more well known people and the Shi'a muslims are called Harazas. Both groups of muslims are very similar including their religion, they both believe in the Koran.The Harazas are usually servants and are mogul descendants. They are often treated poorly and they have nothing they can do about it.
Amir grew up having a playmate, Hassan. They were both the same age and Hassan was one of Amir's servants. Hassan was a Haraza and that didn't affect his relationship with Amir at all. Until, Amir's neighbors began to bully Amir and Hassan frequently. The bullies would tell Hassan that Amir didn't like him, that he wasn't friends with him, that he was only his servant, nothing more. And the thing that bothered me while reading it was that, the bullies were right. Amir only thought of Hassan as someone he grew up knowing. He thought this until he got older and Hassan moved away. This is one of the major cultural differences and it bothers me on a high level.