The short answer is yes he is guilty and the sentence is fair.
Being a doctor means more than handing out drugs. Doctors, especially one so close to his patient, are supposed to be watching for signs of addiction and monitoring their intake as much as is possible.
Murray did neither and facilitated MJ for years.
Times have changed from the old days of "Dr. Feel Good" who just hands out pills. Look at how hard it has become to get things like pain meds for most of us.
Murray wasn't only handing out pills he was administering a drug that should only be given in a hospital, by an anesthesiologist, on an almost daily basis. That is irresponsible beyond the terms of simple oversight.
If MJ was having that much trouble with insomnia why wasn't he being treated for it in a legitimate way?
Every qualified witness testified that he was being reckless and that the drug should never be used in the manner that MJ was getting it from Murray.