I just remembered something that happened to me a long time ago.
I was a young boy, a newspaper carrier for the Pekin Daily Times in Pekin, IL. I had just picked up my newspaper when I was approached by a long-haired 'hippy' type guy who came out of the local McGovern campaign office. He offered me a dime and asked for a newspaper. I explained to him that I only had enough papers for my route, and I could not sell him one. He threw the dime at me and took a paper out of my bicycle paper bag.
Being the same then as I am now, I went into the McGovern campaign office and demanded the paper back. He wadded it up and threw it at me. When I bent over to pick it up, he kicked me; hard. So hard that I flew off the loading dock where I was standing and landed hard on my face. I was crying and bleeding and embarrassed. He was a young adult, I was maybe 10?
I finished my newspaper route and went home. When my dad asked me what happened to my face, I told him. He took me down to the police department and demanded that the McGovern campaign worker be arrested. The police went and arrested him and brought him back to the police station.
I was taken into a line up and asked to pick him out. I was scared and the 'hippy' guys they had all looked alike to me. I kept thinking that if I chose wrong, an innocent guy would be arrested and charged. So I said I didn't know. The police told my dad that they could not do anything since the guy who kicked me denied it and I did not positively identify him.
My dad was furious and told the police that he'd take care of the problem himself once the guy was released. The police told him why wait, take care of it now. They let him into the holding cell with the hippy.
When my dad came out, he was panting and sweating and his knuckles were bleeding and his shirt was torn. The guy was laying on the floor, not moving, but moaning. There was blood on the walls and the cops were laughing and saying 'better get a hose in here!'
We went home and that was the end of it.
Now, frankly, I am not in favor of vigilante justice, as I've said before. I understand exactly how my dad felt that day, though. I'm sorry I wasn't able to identify the guy in the line up, because that would have been the better way to have handled it.
Frankly, if an adult hits a child and the adult is not engaged in self-defense or an actual sporting contest involving himself and the child, I think yes, he should be arrested and yes, he should go to jail. I'd want zero tolerance for adults hitting children (not including minor corporal punishment). Yeah, I'm thinking about how the father of that kid whose nose was bloodied and/or broken by an adult who lost his temper at the match; I'd want something done about it, and that doesn't mean a suspension or a fine.
There is no excuse for adults hitting kids like that, ever. Yeah, it's a martial arts match; but no kid there signed up to be blind-sided by an adult who wasn't even competing.