The easiest way, and at the same time the hardest way, to get Mormons out of Mormonism is to get them to think for themselves. Once you do that, Mormonism falls like a house of cards.
It's the spirit of deception/darkness that has overtaken their minds. And satan is the father of deception/lies. That's their enemy but they, unknowingly, embrace it and it's no wonder they can't receive Truth. However, God is good and if they earnestly seek Him, they will find the ONE TRUE GOD!