This subject has always been in my mind. I was a skinny little kid who was picked on A LOT in school, then it seemed one day I went from being 6'02" and 160 to being 230 and stout as could be. That is when I started to beat up the bullies. I am an introvert mostly, but I get fired up easily.
I have always marched to my own drums, and I have very thick skin. But when I see someone else getting picked on I want to just kick the you-know-what out of the guy doing the picking. Not many people mess with me now days, and I teach my kids to live like that and be themselves. If a kid at school tries to bully them and they punch the kid in self defense or in someone else's defense, they may get in trouble at school, but we reward it in our house.
BTW: The whole Columbine thing was not because they got picked on or were misunderstood. Contrary to the runaway rumors, they actually were the ones taunting and terrorizing others most of the time. You can not pin that incident down to just one thing in the first place. A mixture of bad parenting, environmental influences, mental problems, and many other things are involved in that whole ordeal, but that is for another thread.