The thing about it is, we all KNOW they're clueless.
We're not 12-year-old boys who, on the rare occasion when we're actually paying attention, are using that attention to tempt fate.
We're mostly adults, mostly women, all of us trying to ride safely and sensibly.
And that means being prepared for people to do exactly what that kid did.
I've really been trying to stay out of this thread - I said what I wanted to say on the thread about the crash on the Chicago MUP. But I didn't get close to 5,000 posts by standing on the sidelines holding my fingers. 
Wherever we ride - whether we're on a MUP where the risk is about equal for everyone, or on the road where the risk is much greater to ourselves - we need to be prepared for the likely contingencies. It isn't about fault. It's about safety. We need to be prepared for the right-hook, the door, the left-turner, AND the deranged pedestrian. Because we're just as dead, or just as injured, when we crash with one of those people, as we are when we crash through our own violation of traffic laws.
Inatree, you're not going to hell. And I hope you don't take what I'm saying the wrong way, because I know how scary your crash was, and I know it wasn't your fault.
But the kid was behaving unpredictably and moving quickly. If it had been an uncontrolled dog, you would've come to a complete stop. As I said in the other thread, a lot of pedestrians seem to have less common sense than your average squirrel, yet they weigh more than an average deer. Riding on a MUP means being prepared to come to a complete stop at any moment. (Really, that's true for riding anywhere, but the quarters are so much narrower and more crowded on most MUPs that you have less of an opportunity to swerve or accelerate to avoid a collision.)
I'm very glad you're okay, and that your bike is basically okay (although I agree that getting it checked over is always a good idea after a crash). Take care - and again, please take this as advice and not criticism.
Speed comes from what you put behind you. - Judi Ketteler