You just have to ask them...
“Say, where are all of those Indian converts you mentioned? Because all of the Mormons I know are as white as sour cream!”
“You guys built the Central and South American pyramids??? Why haven’t you built any more? Do you have the architectural plans for those pyramids by any chance?”
They also need to get their story straight on why coffee is so bad. It used to be that caffeine is evil, but they drink Mountain Dew by the gallon ever since the Mo church got stock in Pepsi. Lots of weird superstitions about water, like the devil controls the large bodies of water, that’s why you shouldn’t go swimming.
Going to a university in Utah for 5 years cured me of ever converting. Bunch of arrogant asses.