Yes, I fully agree that everyone should be judged equally before the law. If this had been a black kid from Dallas drunk driving would we be surprised if he got the full 20 years in prison?
I don't think 20 years in prison is an appropriate penalty in this case. I totally sympathize with the victims and their families - but 20 years basically removes this person from ever being able to be included in society. He'll be out at age 37 and basically unemployable. This is exactly how you design a system to increase recidivism.
As heinous as the crime was, I'd much rather see the person spend far less time in jail -1 year to a 16 year old is like 4 years to someone in middle age. Won't he get enough time to "think about what he's done" if he spends 4 years in prison instead of 20?
All that aside, the real miscarriage here is the overly light sentence. But honestly I'd rather have overly-light sentences than overly harsh ones. All should be applied equally regardless of family wealth, class, color, religion, gender, etc.