Far more likely statistically to have been sexually abused by a male family member himself, than anything the mother has done. In fact, I'm not talking specifically about this person, but in cases like this, the mother might well still be protective of him because she knows what helped turn him into what he became and probably feels guilty that she didn't stop it.
* This was supposed to be in reply to the person saying that the mother's over protectiveness is a contributary factor in how he turned out *