This is a conversation that purely took place in my own head. Admit it, you have conversations in your head too. The Mormon missionary in this conversation is pretty much just the sounding board to work through the whole thing. The Mormon will be M and I will be L. I know missionaries travel in pairs, so I'm just assuming only one engages in the conversation.
M: "Hello. Can I talk to you about the Church of Jesus Christ of Latter-Day Saints?"
L: "Sure. I actually have some things I wanted to ask a Mormon about."
M: "Awesome, what can I help you with?"
L: "Okay, I'm going to process through this with you. Your Second Article of Faith says that you believe that mankind is punished for their own sins and not for Adam's transgressions, right?
L: "And if I'm not mistaken, that is at least in part because you believe that 'Adam fell that men might be, and men are that they might have joy.' (2 Nephi 2:25) So the Fall was necessary, and therefore we aren't held accountable for it."
M: "Something like that."
L: "Okay, let's backtrack. You believe that before this world was 'organized,' we all lived as spirit brothers and sisters with our Heavenly Father and Mother."
L: "So, being good parents, they wanted us to be able to get bodies and become exalted like them, kind of like how kids hopefully grow up to be productive adults who continue the cycle of raising children themselves."
L: "So because this cycle had been done before, God knew what the best plan was to make sure this happened, and needed a savior. Jesus volunteered to do it God's way, but Satan wanted to do it his way, which involved basically taking away our free will so that everyone would be exalted but no one would have a choice about it. God and Jesus' way involved almost everyone making it to at least some level of heaven, but not everyone being exalted, because everyone gets to make their own choices, which is free will."
M: "Something like that."
L: "So Satan rebelled against the tested and proven plan because he was prideful enough to think his way was better, started a war that was doomed to fail because he was outnumbered two to one and the other side was led by God, and got kicked out of heaven like a rebellious teenager."
L: "Alright, fast forward to the Fall again. Adam and Eve have to fall. For some reason, they can't procreate unless they sin first--which is weird, since God made everything else able to be fruitful and multiply, and gave them the same command, but apparently their bodies weren't capable of reproduction, or they were but sex is associated with sin even within marriage so they have to sin first. Anyways, that's another issue, so we'll leave it alone. No matter why it worked that way, they had to sin in order to have children, and they had to have children in order for God's plan to work. But God can't tempt them to sin, and since they had no knowledge of good and evil and no sinful nature and weren't spiritually dead, they couldn't sin. They had to be tempted by an outside source. Does that make sense?"
L: "So Satan comes along and tempts them, according to plan. The Bible says he tempts them with a lie, which was that they could become like God or become gods, but Mormon theology says he was actually tempting them with the truth. But that's yet another issue that we won't get into. Anyways, he knew God's plan; God presented it to everyone, including him, and he rejected it, and doesn't want God's plan to work now because of his pride. Everyone who knows much about the Bible knows that. Yet for some reason, he played along with God's plan and did exactly the one thing that God himself could not do; he tempted them to sin. Wouldn't he have left Adam and Eve to be sinless forever if he truly wanted to thwart God's plan?"
M: "Well, uh...you see...I..."
L: "You don't have to answer that right now, there's no scripture for that one anyways. I'll move on to another related question."
L: "Okay, so we agreed earlier that in Mormon theology, the Fall was necessary to God's plan?"
L: "So sin was necessary, so that we can be tempted and prove ourselves and apparently procreate and all that."
L: "Okay, the Bible says something different, so bear with me here. The Bible says that sin was not part of God's intention for humanity. He made creation good, and then we sinned and fell, and now God has a plan to redeem us. Sin is bad, redemption is good. He could leave us in this state because we got ourselves into it, but we can't get ourselves out, and He is a loving God, so He's made a plan even before He made us to get us out of the mess that we got ourselves into. But sin was not necessary. He gave the command to be fruitful and multiply before the Fall, and He meant it. Satan lied to Eve, and she fell away from God's plan and mankind became spiritually dead, and we can only be made alive again in Jesus. There's no becoming like God or preexistence, there is redemption from a fallen and sinful state to the perfect creation that God originally made. We will be cleansed of all sinfulness and corruption. That's the plan of salvation that the Bible outlines. I know its not what you believe, necessarily, but its what the Bible says. Are you tracking?"
M: "I think so..."
L: "Good. Okay, so think about a rape victim. You probably know one, if you're willing to get personal about it. About a fourth to a third of women are sexual assault victims, and about a sixth to a fifth of men are, so chances are you know at least one, probably a woman."
L: "Alright, so let's look at the rape they underwent in light of the Mormon view and the Biblical view of sin. In the Mormon view, sin was part of God's plan. He doesn't necessarily like it or what it does, but he planned on it and requires it. So if we get very literal and down to the very core of the issue, when that rape victim you know says, 'Why did this happen to me,' the Mormon view would have to say, 'Because sin is part of God's plan, and not everyone resists temptation, and you became a victim to that.' I know that doesn't sound good, but when you get down to the core of it, that's true, right?"
M: "I guess..."
L: "Now if you go to the Biblical view, when the rape victim asks that question, the Biblical Christian can say, 'Because this is a sinful and fallen world, but God can and will redeem and restore it, and that includes redeeming and restoring what happened to you, if you let Him.' That sounds a lot more right and hopeful, doesn't it? More in line with the nature of a loving and perfect God?"
L: "And that is one of the reasons I can't accept the Mormon God. I can't accept a God that would tell a rape victim--and I know many--that what they underwent was part of his plan in the sense that he meant for sin to come into this world. I can accept a God that did not mean for sin, but knew it would happen because we were able to choose it and He is all-knowing, and then He made a way to redeem and restore, which He is doing through Jesus.
"And that, my friend, is the true gospel."