in my opinion, poor behavior in children is a result of the parent.
yes, certainly there are a number of outside forces that will influence a child, whether they be 2yrs old or 17yrs old, however as a parent it's your duty to make sure your kid understands.
think of it this way;
your family is a caravan, you're the leader of it and you're traveling through dangerous territory. it is your responsibility to make sure the people in your caravan are safe, so you have to instruct them on how to behave in this new land or else they'll die.
it's the same as educating your children on drugs, fiction vs reality, sex, etc. You also have to judge what level of each is ok for your children.
Santa Claus is fiction, yet many parents choose to let their kids believe the fiction is real, when these kids do outrageous stuff that is inspired in a fictional reality, it had to come from somewhere.
Now I'm not blaming Santa Claus for inspiring video game related deaths, I'm blaming the parents who allowed such illusions to exist.
I myself am a father, and while I will tell my kids about Santa Claus, I want them to understand that he is a character and not a real person, and that no one person could actually fly around the world in one night and deliver presents to everyone.
Many other parents don't like to say "I'm to blame" because it makes them feel like they've failed their family, and their life, especially in an economic world that requires both parents to work. It seems that in these days providing for your family simply means "paying the bills" and not actually treating them like your famliy.
anyway, we're getting severely off topic again, so perhaps a new thread is in order?