I know a few friends who got serious brain injuries from stupid fights. You get punched, knocked out, and you fall and hit your head on concrete... even minor fights can have lasting consequences.
I was bullied to shit at school, all anonymously (pre-internet era)....urine soaked chocolates put through my front door, cans of drink emptied and refilled with urine, someone even fired an air rifle through my front door one weekend..not all bullying is "easily" solved by retaliating in kind, and punching someone will have fairly heavy consequences as an adult, so perhaps it is best to learn other ways of dealing with it..."But he started it" does not cut it if someone bullies you at work.
(incidentally, I later found out that it was my "friends" who had been doing this)