Thankfully such jerks are rare, but they're out there. It's re-assuring when the parents are on the ball though. This past weekend, I was sitting on a bench, with my helmet beside me. A little boy (probably about 3 or 4 years old) came up, and he started feeling and tapping the helmet. His parents quickly shouted over to him to stop. It was fine in this case, but I was pleased that his parents were right there and keeping a watchful eye.