I suppose you could try to use the "If the only reason your doing something is game mechanics, you're probably doing it wrong" philosophy with this. If the only reason you're forming your "it's-not-a-religion" religion is to keep real religion from coming into your realm, then the only reason you're doing it is game mechanics.
Perhaps some parallel could be drawn to declaring war on another realm, and then sending message saying "We're not really at war with them, we just needed to declare war to take this region. But really, we're still friends."
