Our instincts are flight or fight. We may flee for a time, but we are looking for a chance to fight whether it is with guns, fists, cars, or words. The fifth commandment says you shall not murder. Teaching that violence solves problems can kill. Violent play and entertainment can kill.
Exclusion can kill.
Ostracizing can kill. Bullying can kill. Teasing can kill. Words can kill. We have a culture that accepts and tolerates these more subtle forms of killing much to easily, and when it erupts into physical death and chaos, we are shocked.