If you look at the pictures of the girls, the attack was brutal. But it also appears that these girls had been following him around, taunting him for a while. He needs to be in jail or perhaps a mental institution. But this also should serve as a lesson to kids who pick on other kids that when you push someone to the breaking point, bad things happen.
No, this guy has problems. If he had teased back and said “which one of you is Hermione and which one’s Ginny” or something like that, it would have shut the two girls up.
I remember reading a few years ago of some schoolgirls who ended up getting stabbed (non-fatally) by a man on the bus who they had been taunting who had severe mental health problems. Naturally, the man was sectioned under the mental health act and as far as I’m aware is still in an institution, where he belongs.
Having said that, I recall the fact that I didn’t have a lot of sympathy for the girls, who were clearly the aggressors and the partial authors of their own misfortune by taunting someone who was clearly a very troubled man, but then again, I suppose they did a public service by making sure it they were the ones who provided the excuse to get him locked up, rather than perhaps some more innocent people who might have ended up getting hurt somewhere down the line...