Even if one is "not of their right mind," one must still do what they need to in order to protect themselves.
A drowning man may be in a blind panic, and "not of their right mind," but you don't allow them to pull YOU under with them. Similarly, an alcoholic or a drug abuser or a compulsive gambler -- at some point, based on their treatment of you and your children, you have to say "I love you, but YOU NEED HELP. Until you get it, I can't remain here with you anymore."
I think PEI's "hate to sound cruel/cancer" answer is perfectly reasonable.
