I disagree. If a person commits an act in good faith, and has know way of knowing of bad consequences of the action I would not assign any moral responsibility or blame to that person. The person of course, was causual to the act in that if he had not done what he did it would not have happened. For example if a doctor is operating on a patient, no one knows the patient has an allergy, a test even failed to detect the allergy, and while operating the allergy causes complications that kill the patient; I do not blame the doctor.
I don't see anything in the article that hints that when Huckabee commuted his sentence he knew the person would commit violent crimes. None of the crimes listed mention a victim being harmed, although at least one crime included gun possession. If you have some evidence that Huckabee was at least partially aware that this criminal was more likely to commit more violent crimes than any other juvenile sentenced to a life sentence I would agree with your position. I am not saying there is no evidence, but I have not seen any presented.
I also don't see how specifically commuting a persons sentence is more responsible for that persons crime than a blanket reduction in sentences that would ensure that no juvenile offender would ever be locked away for life; no matter how heinous his crimes and no matter what evidence there might be that he would commit more crimes. In fact, Huckabees action of reveiwing the cases and releasing only the ones that appear to be safe and have a chance in the real world seems to be the most responsible.