The problem with your explanation is that it presumes that people are going to be screened or tested at the door to verify whether they have sincerely held religious beliefs. Absent that, I think it's safe to assume that anyone who hasn't gotten the vaccine is going to claim religious exemption in order to go to the theater.
As to the idea that Christian Scientists are not whack jobs, some of us might not agree with that assessment (but then I tend to question the sanity of anyone who is a fundamentalist of any religion).
