That he hurt you because he had BPD makes about as much sense as that he committed armed robbery because he was diabetic. IDK, maybe he couldn't deal with not being able to have sugar, so he decided to hurt and traumatize someone and take something from them, in a misguided attempt to get what he couldn't have.

Hurting someone doesn't make him any more likely to be able to have fulfilling relationships either. Who knows what it was that he thought he wanted. There is no excuse for what he did.

And the majority of diabetics probably don't commit armed robbery, either.