I cannot think of anything more self-defeating than a “religious exemption” enshrined in law.

Anyone who professes any religion – anyone who cares about any religion – should really, really, really not want the government chiming in on what qualifies as legitimate orthodoxy or orthopraxy.  That is a task for your priest or your prophet or your guiding angel, not for an agent of the secular state; and if you let the state’s agent make the call, at some point you’re going to find yourself very unhappy with what he has to say.

Anything that a believer should be allowed to do, in the name of his faith, is something that anyone should be allowed to do for any reason.