I believe that the judge and the jury who heard the young man's case were in a position to accurately assess the man's culpability and maturity. I do not support the mentality that believes serious consequences must never be meted out until age 18, sorry - you'll have to try to sell that concept to someone who was never on the receiving end of violent juvenile offenders - which I personally was as a child.
Whatever your subjective view of these things, the law is the law. 17 is still a juvenile, no matter how big a criminal we are talking about. (And this little punk borrowed mom's car without asking). He was still a kid. He was 17. The law is the law.