This topic has been debated to death in the 3 years I have been reading this site. Do a search of posts on the word "disease" and you will get hundreds of threads. There is no black and white answer to the question.
But, you know what? It doesn't matter unless you are the person working for the insurance company who approves the claims for treatment.
Disease or not--is it okay for you that someone treats you badly? Does it matter what causes someone to behave in an unacceptable way? You are the one who makes the choice of who you have in your life. Do you want this person in your life? Do they enhance and enrich your life? Or do they diminish it? If you make your decisions based on behavior, then it doesn't matter the cause of the behavior.
L