I say this as a sufferer. One who was in his psychiatrist's office two days ago, complaining about the fact that the angry part of me has been isolated and suppressed for the last twelve years.
The first rule of saving someone else from drowning is "Don't drown yourself." The first responsibility of the would-be rescuer is for their own safety - two drowned people is worse than one.
So, if you're a supporter, and your sufferer is a danger to your safety (mental, physical), your first obligation is to protect yourself. That means that you can't accept responsibility for the fact that the sufferer's rage is explosive.
I have 12 years of distance to help me say this, but the best thing my first wife ever did was leave. I hate the fact that she left, and I haven't entirely forgiven her for it, but it was better than the alternative.
I get that sufferers need help. I get that the worse the violence is, the more desperately we need the help, and I know what it's like to be watching out my eyeballs like a helpless prisoner, while my arm is throwing punches. And when she was gone, I felt worse. And I started getting better.
I'm angry and frustrated that (almost) nobody helped me when I needed it most. But the people who were able to help me were the ones that I wasn't threatening (one way or another, I was no danger to them). The first step for a sufferer in the situation described above is to make a serious to become safe. And the first step for a supporter is also to become safe. The days when relationships were expected to withstand a few beatings are over, and that's a good change.