ironically, it takes a lot of empathy to make a good insult. you need to be able to put yourself in that person shoes. its not exactly healthy emotionally, in the long run.

i'm a very good insulter, (i don't know if that's a word, english is not my first language) i developed it as a defense mecanism, since i was bullied in school (not highschool, i was pretty good at it by then). as >>6 said, you need some kind of trauma to be able to pull it off.

if you're going to hone your insulting skillz, be careful, you may lose control over it. i sometimes say some pretty nasty stuff to my friends when drunk or annoyed.