People put others down for a whole mess of reasons. Saying they do it because they are insecure is just stupid. Sure some may do it because of that, but alot of people say that just to make the bullied people feel better about themselves.
Bully's won't admit the real reason why they're bullying others, they'll probably just say it's fun or they like doing it. Idk there's so many differnt reasons why they do it; family issues, low self-esteem, they think they're better etc. So yeah. :3