It is a parent's responsibility to explain the rules of behavior to their children before they allow them to do something as dangerous (to themselves and to others) as riding a motorized bike on the street. Since that's what the kid was doing, it's pretty apparent that the parents already aren't keeping a close eye on the kid. Or perhaps they had already explained it all to the kid, and he chose to ignore them. Hopefully, the cop incident made a stronger impression on him than his parents.

I honestly think that a run-in with the cops at age 7 isn't horrific if you've already been taught what's right and what's wrong. By age 7, I knew there were various consequences for doing the "wrong" things. I got chastised by cop when I was pretty young for skate boarding in my neighborhood because I wasn't being careful and riding it straight out into the street. Yes, it IS intimidating to have to deal with cops at ANY age, but it's a lesson I never forgot.