Has it ever crossed your mind?

Why do some people bully? I came to the conclusion that there are a lot of reasons why one would decide to bully. They might have family problems going on at home causing them to act up, having no friends and feeling lonely as a child he/she might have been an outsider never able to fit in with any of the kids at school and build up frustration, etc. They also think that using differences as an excuse for their bad behaviour, when I say difference I mean things like jealous, envious, insecure, afraid and etc. But what they same to forget is that differences makes a person interesting and unique.