Bingo. Someone gets it.
Some very competent psychologists, specialists on the human brain and development of children's psyche (and sense of identity), have examined very closely the development of the synapses, of different parts of the brain (ruling over faculties such as reason and empathy) and their interconnections in regards to our awareness of ourselves and others, of what could be summarily understood as our understanding of right or wrong, the basis of which could be loosely defined as ''moral behavior'' and the responsability that we have towards our own acts.
What they have found is that most if not all children and teenagers from 0 to about 16 have not reached a sufficient level of development cognitively speaking to comprehend all ramifications of any act of theirs, and that the part of the brain that governs over empathy is still largely underdeveloped at that time, meaning that the overwhelming majority of them are incapable of truly taking responsibility for their actions, putting themselves in other people's places, and must thus rightfully defer to their parents or legal guardians in most cases. In short, teenagers have only slightly more judgment before 16 as your full-grown adult does when drunk, but obviously better faculties.
Think about that for a second before you hand out car keys to your kids or leave them with too much freedom. I'm not saying to sequester them, no, but keep a close eye on them until the are 18+ and ready to live on their own, then give them advice (that they will shrug off and not listen to) and let them go while being ready at any time to cushion their fall when and if it happens. That's basically modern parenting 101 in a nutshell.
Anyways, Miller will or will not become a better person, and it will depend on his own self-awareness and effort to change going forward, but we should not be so critical on him based on what he did as a much younger kid.