They deny the eternal deity of Christ. The foundation of Mormonism is a false depiction of the Father and Son as Smith’s own variations of the Greek mythologies. Again, the Jesus they portray is an impostor. That’s been the problem all along. While the Catholics may struggle with the steps subsequent to the established and genuine facts of the proper ordination of the Trinity, crucifixion and resurrection, the Mormons can’t even find the dance floor. If I come to you and present the story of Alexander the Great, then explain that he was a dude from Nebraska who smoked a lot of pot, decided to conquer the known world before he was 30, and quit his job at Walmart to do so, then he went on to forge an empire from Hannibal, MO to Tampa, FL and wept when he saw the Gulf of Mexico because the sight of girls in bikinis was too lovely. You can believe it, but it isn’t the story of Alexander the Great. If you put your stock in the Mormon depiction of Christ, you are deceived about His identity, and incapable of believing in Him or His work until it is presented accurately. You are therefore wholly ignorant of the person in whom you claim to believe, and necessarily not believing in Him.