Ask them if they send or donate any money to the Mormom Church.
Also ask them if they knew the founder of the Mormon church was a convicted con man!
And ask what they think of the fact that when their tax exemption was going to be yanked in the 70s, the grand poobah "had a vision" that it was suddenly ok to have black deacons (or whatever they call them).
You might also suggest they read the Sherlock Holmes story A Study in Scarlet.
In the LDS church, priesthood is conferred as a matter of course on men and boys in good standing, age 12 and up. It's a requirement for leadership positions, as well as for reaching the highest levels of heaven. This is a reason why the convenient "revelation" in 1978 that it was OK for Blacks is such a big deal.
Why did Joseph Smith make up at least 3 different versions of the "First Vision", and why did later leaders pick the most outstanding one to claim as the one and only "First Vision"?
Why did Joseph Smith send several men on missions and then "marry" their wives?
Why did Joseph Smith lie to his wife and other members of the church about "marrying" other women until his wife and others become irate, then conveniently have a" revelation" from god, condoning Polygamy?
Why does the DNA evidence contradict where the Book of Mormon says the native americans come from?
It isn't "Mormon," it's "Mormom."