I think you have to make a distinction between kids play and adults when talking about 'bullying' and the non aggression principal. I was bullied a little in school and it made me think about how to defend myself. The far greater harm would be if the Teachers and adults lock down the school experience and prevent kids from interacting.
Is sarcasm and irony, any kind of humor bullying? We need to have a better definition of the word. It really annoys me when there are these loosely defined words that come up and mean different things to different people.