There's a difference between instilling your own moral principles upon someone and actually helping them.
Their only idea for solving the problem, in retrospect, is to remove from his life the only thing he cared about!
You can help someone in more ways than just "raising" them, and in this case the way to have actually helped him would have been to display enough understanding to gain his respect, and then guide him gently into a safer course.
Even in an article that's published in a paper with fact-checkers and standards, his parents still refuse to acknowledge RollerCoaster Tycoon as anything other than a violent video game! It's a game about building a theme park! It is blatantly clear that even the mildest effort to understand him or his activities wasn't taken, and that they refuse to do so even with the benefit of hindsight.
You can stand on a hill and grandstand to your child as much as you want, but if you don't put in the slightest effort to understand them it's your fault when they end up doing something that hurts them.