I don't mind some light hearted mild bullying like we have now (call someone a llama, be rude, get into fights etc) I wouldn't be bothered by some more negative interactions, but I wouldn't want to see bullying in the true sense of the word.
I don't think it would teach kids anything, I think most kids would find it funny to be a bully sim, or even control a bullied sim, because its not real life and the animations would have to have some sort of entertainment factor (my daughter finds making a sim wet themselves in public hilarious, she also finds the way sims end up in a cloud of dust when they are fighting hilarious, so if she had more ways to make her sims life a misery she would be entertained for hours, I dread her cottoning on to the fact she could kill her sims off) Now in real life she wouldn't find it funny, and she regularly stands up for kids around her who are bullied, but in a game it wouldn't teach her anything other then more ways to cast misery on her poor sims.
I don't think a game could teach the effects of bullying in a good enough way, its down to the adults in the childrens lives to teach them.