I would have been among those not to even have noticed. Had I even seen it I wouldn't have given time to even pondering it.
It really doesn't surprise me though that people were rude. When you have a child who acts unusually as a result of autism then when you are among a large group of people you become the focus of stares and comments. I just ignore it these days.
Try having a kid with autism acting unusually AND wearing a full arm cast (because I decided to buy the kids a trampoline for Xmas
) AND drinking a "diet" shake.
He was being unusually well behaved this morning though, otherwise I imagine the reactions would have been much worse.