As Village Idiot says, its a bit harsh but none of us have walked in your shoes. I think that our parents worked with the skills they had at the time and at this late stage of their life, telling them to leave the cult would be hard to do. If your parents are like mine, their whole network of friends are jehovahs witnesses and its not that easy to cut all ties.
But then you have to do what is good for you and what you think is right.