a marriage is a partnership and we went into it to help one another.
So where your logic fails me is when one part of the partnership stops being a partner and instead is trying to destroy the partnership. And you can not control this partner only you can control yourself. This is where DB steps in. It likely is similar to AA and the idea is the LBS has been a codependent enabler just like in AA. The point is to learn how to stop this codependent behavior, IMHO.
Good luck 2lady, hope you find what you are looking for.