Sounds like the parent is upset because someone *dared* tell his little angel "no", and then called it discrimination after the fact.
There's usually a range of expected/acceptable behaviors depending on the establishment, and disability or not, you can't go into an establishment and let your child run wild and not expect someone to say something about it.
If I saw a kid spinning around on a concrete floor, I would absolutely be concerned about him getting hurt and bouncing his head off the concrete. If the parent can't control the kid's behavior, then it's time for them to leave, and then possibly go somewhere else where that behavior is actually acceptable.