I've had kids look at my bike and parents letting them walk around it but never have the let their offspring hop on it. If I'm there I will say it's OK if the parents want to set the kid on it for fun. Thankfully it's never happened to me.
Once I was parked outside of a Hooters and these guys backed their car into my front tire and pushed my bike back about a foot, bending my kick stand down to where it almost dropped the bike. A couple on the outside patio came inside to tell me, since they had seen me park. The dudes friends tried to say " how do we know it wasn't like that before"? I was ******* furious! I said look mother ******! They saw you *******! now don't move, I'm calling the cops! Luckily the guy who was driving had more sense.