For example, the religious organization has an interest in permanently maintaining data regarding an individual’s status as one of Jehovah’s Witnesses. Deleting such information would unduly infringe on the organization’s religious beliefs and practices.
This is what you could contend, which is, that what they need is only the information necessary to establish your status with them. They don't need all your data for them to know that you are no longer a JW (or that you are, for that matter).
This is why that religious exception nonsense should not be allowed. Of course, many people like those exceptions when it comes to discriminating against those they don't like, but then complain when it impacts them.