Experiences do not provide the moral values you need to understand what is right or wrong. I agree experiences can shape you as an individual and your views, but to suggest people have not matured until later in life until they obtain more experiences is not accurate.
I am not on board with the argument that you need a host of life milestones to be considered an adult.
You're mixing two different sets of measurement of a person though, which is confusing the matter.
Morals and values are things that are taught by parents, family, friends and teachers. Yes, they influence our decision-making, but only in so far as how important morals and values are to us as a person.
Experiences shape our decision-making in a much more subtle, but direct way, and the learning acquired from experiences cannot be obtained through any other means.
As an extreme example, the main character in the movie "Nell" had very strong morals and values because her mother drove home the lessons contained in the Bible. HOWEVER, she was still very much a child because she lacked completely in worldly experiences - which is why she was able to be tricked into lifting her dress up over her head by a person who wanted to exploit her innocence.
Also, as the mother of 2 autistic children, I can absolutely suggest - with certainty - that some people do not mature until later in life and after they've obtained enough experiences - an unfortunate reality is that some people with severe disabilities never reach maturity. Developmental delays directly affect when a person is ready to experience new things, and a person who lives with them is younger emotionally than their physical age. Using one of my own sons as an example, my youngest is 8 years old physically, but emotionally he's very much closer to 5 or 6 years old and when it comes to issues of personal safety, more like 4. As of today, I can't trust him not to overflow the sink or tub, or to play in the yard without wandering off if I don't check on him at regular intervals or at the very least make sure his older brother is outside with him.
As far as BDD goes, I am not suggesting that he has developmental delays or that he is not an adult. What I am suggesting is that he is emotionally very immature and that his experiences are lacking in terms of behavior and consequences, which is evident in that he's still behaving this way at his age. Perhaps if he'd faced more severe consequences last year, or while he was growing up, he wouldn't be in the situation in which he currently finds himself.
ETA: He could also just be a complete idiot that thinks his parents' money gives him the right to do whatever he wants.