Most abusers resist getting professional help very strongly although some may attempt to manipulate the therapist to their advantage and sometimes succeed in this. Do not however resort to violence yourself, except in self defense. When setting limits or asking a person to respect a boundary, there is often a debate designed to make you cave in or change your mind or make you feel bad, guilty and unreasonable. In my office I invariably meet people in families interacting along these lines. Sometimes it feels more like a courthouse with opposing attorneys and prosecuters presenting their cases with mountains of evidence to prove the other party wrong.
Abuse takes away choices from people, love gives choices.
Offering choices, suggesting alternatives can empower the abuser. I know this is counter-intuitive but as explained above, abusers are really powerless and depend on others for their needs and avoidance of anxiety and upsetness. Empowering them offers them ways to meet their needs without outside help, and offers them ways to cope. Abuse is a tool for the abuser and it will be used unless other tools are given to them that will get their needs met or make their needs less important. Using the word addiction as a metaphor to help us understand our behavior in a relationship can be useful.