Enlighten me is correct. Violence isn't really a part of the disorder. But people with BPD do struggle with impulse control. So if they feel like doing something, most of the time they just do it. Combine that with extreme, intense, emotional lability, you can end up with someone that can easily become violent if that's their predilection. But it's really about each individual. Some people are violent, some are not. Some people with BPD are violent, some are not.
I came to many occasions in which he would drink and then become violent.
Also keep in mind, some people are just mean drunks. It's just how alcohol affects them. Does your ex become violent when sober, or is it just when drinking?