If they break away from the abuser, they stand no chance at all against the Smear Campaign the abuser then launches. Partially because they believe they -were- wrong.
This does not mean that the reaction was okay. It is never okay to treat another person with violence. However, it is understandable. And it is very important to differentiate this kind of reaction with the kind of ongoing abuse that causes it.
I don’t think it’s fair to call Reactive Abuse “abuse”, because the word implies a severe violence that causes detriment to the mental and physical well being of the victim. “Reactive Abuse” almost never actually harms the true abuser it was aimed at – in fact it is often exactly what they wanted, and only bolsters their sense of self-righteousness and fuels their power over the victim.
A good way to tell a victim who reacted to abuse, and a psychologically abusive person creating a smear campaign against a victim is their attitudes toward their own actions.
Victims will almost always be able to admit their own faults. They will know they reacted badly and did wrong. This quality is actually what the abuser uses against them in the first place to make them believe they are the ones in the wrong. Part of healing from abuse is learning to point out which of the abusers behaviors are, in fact abuse, while still acknowledging what you handled badly. (And everyone reacts badly to things when under the extreme pressure of abuse!).
Abusers will almost never admit they have ever done anything wrong at all. Their victims will be blamed for everything. They will hold every tiny thing against the victim, even things they could not possibly control, or they have never tried to talk to them about. They use social bigotries against the victim, and in their own defense. (Especially mental illness is used in this way – they believe their own illness excuses them from every wrongdoing, and their victims illness is proof they are in the wrong).
The most dangerous, most intelligent psychologically abusive people will even try to fake being able to admit their own mistakes. But they almost always get tripped up in the details, by claiming “oh I handled that badly -” but following it up with “-but only because of (something that is the victims fault after all)”.