Its more about how kids/people process information. Its certianly possible without any supervision to process morality, a kid could think its ok to act out violently when not threatened.
This argument has been used with books, moives, music and now games, yet all of these are refelections of our socities of humanity.
Of course a kid could, just like a kid only exposed to religious zealots would think its ok to kill Medical Dr.'s here in the US, or Israeli's if they Muslems, its all around us, of course only in the extreme fringes. So it is possible.
The most important aspect is education from a social/moral (that doesnt mean religion) context.
If in our society, parnets are too overwhelmed trying to survive then its up to the government to fund educational awarness for kids.
I could see it for kids under 12, but it get touchy after that 17 is almost old enough to be sent to war to kill people for REAL.
Thou it is incressingly tougher, exponentialy the longer socieity waits to teach these things like morals.
Of course many parnets say they dont want thier kids learning morals form the goverment (ie schools) but it is becoming extremely obvious that many (certianly not all) parents arent/cant/wont teach there kids. Even if its only 25% that translates to huge numbers.
But I don't get a sense you're listening, so, fuck it, let's go to Hell !