My question is this, am i a bad man for not letting her see them?
I'm not your judge, so I'll only state my opinion based on what I read. You are not a bad man. Apparently the courts and professional counsellors agree that she should not be in contact with them.
She was an abuser, is still unstable, and could be an abuser again. On one hand, it may be okay for her to see them. However, it may be extremely traumatic for the boys to see her.
Consequently, I don't see it as an issue for her to decide. When your sons are mature and well-balanced enough to deal with seeing her, it will be their decision whether they do or do not want to have any dealings with her.
Like I said, it's just my opinion.