Nobody worth their salt likes to toot their own horn on this topic, but since you asked, I'll go first.
My neighbor's grandson had just reached the age where gangs looked tough and glamorous. Despite living in a rough neighborhood, he was basically a good kid. He was just being lured in, and his mother couldn't keep an eye on him all the time. With no father around, she had a hard enough time watching the younger kids.
Joey liked to talk to me because I knew all sorts of things. When he started talking about his "bad-ass" friends, I decided to nip it in the bud and took him inside my living room where I brought out my guns. I unloaded each one and threw the safeties. I gave him a course in gun safety, showed them how they worked mechanically, and let him take one apart and put it back together. I showed him how to hold one and hand it to another person in a safe and reasonable manner, all the while emphasizing that there is precious little difference between a gun and a hammer. They are both tools designed to do a job, after all.
Then I let him borrow my books on gangsters. These were the big boys; Al Capone, Machine-Gun Jack McGurn, John Dillinger, Bugs Moran, Dion O'Banion, Big Jim Collosimo, Johnny Torrio, Baby-Face Nelson, Pretty Boy Floyd, and of course Bonnie & Clyde. I showed him the photos of the Saint Valentine's Day Massacre, including the one taken from the back of the garage that clearly shows a man's brains spilling out onto the floor, his lifeless eyes staring at the ceiling.
Maybe Joey was too young to deal with these images in a tough-guy way. He brought the books back to me, shocked at the fates of these "tough guys". Most of them died in less than glamorous circumstances. The comparison of these hot-shot mobsters with the paths that his "bad-ass" friends had chosen was not lost on him. By being allowed to handle a gun, to learn about it, and to understand what they are, took the mystique away. He is no more fascinated by guns now than he is by a circular saw. And the gangs? He tells me that he has better things to do with his life. He wants to become an anthropologist.
That's one more kid society doesn't have to worry about.