You're right, two wrongs DON'T make it right.

But it was also wrong for his parents to seemingly turn a blind eye to their child who probably was reaching out or crying for help long time ago before the attack, and didn't really know how to go about doing it.

But if he were MY child, yes, I'd fight tooth and nail to get some help for him and get him into a program, even if it means he has to serve his time. I'd also fight to get him out of there and into a youth program or institution to get him some help!