Indeed.
But that doesn't mean we shouldn't be able to disect Mormonism, especially when they claim to be Christians.
Seeing as how the Vote-for-Jesus crowd is currently supporting Mike Huckabee, forgive me if I consider their dissecting abilities a little suspect.
But we can if we want to. What if a Satanist were running? Article VI applies to the government, not to the voter. In fact it exists to protect the voter, to protect his right to vote however he darn pleases.