Oh, I'm not advocating the use of violence to correct criminal behaviours, though I realize that it might have come across that way. I was just thinking that the entire scene seemed to be making light of what the skating perverts were doing. Oh hi you molest people and steal their underwear off their bodies? You can't just buy them from a store, lololol.
They were purely being a nuisance though, calling what they did molest is certainly overdoing it. Their actions mainly seemed to provoke outrage and anger.
And in assulting them violently Knuckleduster suddenly turned into the biggest criminal. Those morons should just quietly have been arrested by the police. And dealt with by the normal justice system.

I agree that gentlemen would make a fine hero if he wasn't a quitter in his youth.

Basically the only hero school exam we saw is related to Yuuei, which is the top best school in the country. I assume there are many lesser schools with hero program that doesn't need you to defeat a giant robot for its entrance exam.
I do think calling him a quitter is a bit unfair. It does seem fairly clear that the schools to a large degree judge people on the strenght and utility of their quirks. And Gentle-Man just dont have a really useful one.