Of course I would go into a burning building. In your new made up situation, which is entirely different than the original slappy one, I still would not react in the way you're intimating that anyone would. I am not irrational or violent. I would, while screaming bloody murder, go to my child and scoop up my child/tear him away from the fart. Then hope I charged my cell so I could call the police right there. My thoughts would be towards my child and getting them to immediate safety, not beating on the slapper grabber.
Now back to the unemotional response intimation. Perhaps, but I prefer to call it realistic. I am well aware that none of my children are precious innocent snowflakes, and my very first reaction on finding my child being slapped by someone else would be and has been to turn to that child and ask them what they had done to get that smackdown.
/has a witness