If his parents were already teaching hate, this could have made their belief more solid. Or if they didn't have hate in their hearts, that situation probably changed their views. People have hated all kinds of ways, not just racism. Some people hate others because the other people have better things than them. Others because more girls like one boy than the other boys.
Hate comes from home, and many parents teach it.
It also comes from children misunderstanding the stories their parents tell. My dad could have talked to me more about what his story meant and about what it made me think and do. From my experience, I learned that I can promote peace by loving all brothers and sisters and by communicating clearly with everyone.