The prison society mirrored the "home society" since the outside world was divided into two different racial groups and that's how the prison society was portrayed too. The prison society also had assigned jobs for each inmate as if they had to work for their keep how the outside world is. I think ten years after Danny's death, Derek would still be on the right path towards equality and would have a job that he worked hard at. Instead of Danny's death affected Derek in a negative way, I think that Derek would be able to turn it into a positive and be able to help young rebellious teens like Danny.
I think the turning point of Danny's life into racism was when Derek and Danny's dad told Derek that he was proud of him for having racist opinions. Any young kid will want to please their parents no matter if it's wrong or right. So, the main factor that Danny got killed was because Danny became a racist on the outside to make his dad and Danny proud, however, I don't think that Danny was ever truly racist. What I think that Doris and Davina symbolized in the movie was maybe police force. You never see much of the police in the movie except for the scene where they arrest Derek for murder. Doris and Davina attempted to speak up a few times in the movie, but were always silenced like the police were.