maybe the parents need to keep an eye on their visibly autistic kid in public.
and teach your offspring not to touch other peoples things.
If they can't learn to not touch other peoples' things (and keep their hands to themselves generally) ...
well ...
We have places for people like that. Very special places, where they get a small room, and a bed, and they get fed every day, and they can occasionally make phone calls! They will, of course, be carefully guarded ... and we the taxpayers foot the bill for all of it.