This girl is 11-12 years old. The man is 6'5" and 250 lbs. That punch in the face could've killed her.
Remember this recent story of another music teacher who punched a 14-year-old boy in the classroom: Maywood Music Teacher Punches Student That boy wasn't punched as hard, and many people sided with the teacher, but the teacher was arrested and charged.
Is the guy supposed to wait until he’s on the ground with them kicking him in the face?
The herd mentality is strong. If she would have successfully struck him (they had already attempted to push him at least once) then what is the likelihood they would have swarmed? Highly likely based on past other incidents. So the solution is to diffuse the situation at the soonest opportunity, which he did. No further attack. Actions have consequences, and the girl got hers.
“That punch in the face could’ve killed her.”
If only. That would be one less convict whose three hots and a cot we’ll be paying for five years from now after SHE kills someone.
The fact that she's alive and declined medical attention indicates he didn't hit her as hard as he could have. Shoving her away just resulted in her charging back, so it was time to increase the level of force.