Yeah, and playing violently should not be allowed. Maybe if we taught children from a young age that guns were bad, people wouldn't go around massacring each other in this country.
In a study of adults who committed violent crimes (including the Virginia Tech killer), it was noted that their childhoods were marked by a
lack of play (including violent play). "Play can act as a powerful deterrent, even an antidote to prevent violence. Play is a powerful catalyst for positive socialization", according to psychiatrist Stuart Brown. The Lucy Daniels Center for Early Childhood encourages parents not to suppress aggressive play. "Children turn to play so that they can learn what they need to learn about aggression. We should become concerned about children's relationship to aggression only if they appear to be overly pre-occupied with aggression in their thoughts or actions
outside the sphere of play." 60 to 80 percent of boys and 30 percent of girls played with aggressive toys (including toy guns) at home.
TL;DR: studiest have never shown any kind of link between playing with toy weapons in childhood and violence in adulthood, and there may actually be a link between a lack of play and violence.