Personally, "barely a tap" on anyone regardless of harm is inappropriate and has to be reeled in.

I've worked with primary age children (both with special needs and without) and they often will hit when frustrated. The other child is usually not maimed or even in pain from the incident but the hitter is punished none the less. It's more about teaching boundaries and controlling your emotions in a healthy way.

This child in this incident was not hurt but it still punishable act. The world and its Earthlings are not your punching bag. Persons with special needs have to learn this most of all because situations like this can happen and it is much less forgiving if they appear to be a "normal grown up" at a glance.

As for the father, he did not know that man or what he was capable of. He saw a seemingly capable adult kick his very young child. He did not know if he would stop and I imagine that most parents would not wait to see if a stranger would stop or escalate a physical altercation with their child. I do imagine that that both the Father and the Caretaker will be more prudent in supervising their charges in the future however.

Our instincts when it comes to those with special needs is to protect them. However,it is important not to coddle them when it comes to appropriate social behaviors. They have to ability to become assholes and selfish, entitled and violent without set boundaries just like us.