Because he testifies of himself, "Before me no god was formed, nor shall there be any after me." (Isaiah 43:10). Inspired by the Holy Spirit, David testifies of him, "Before the mountains were brought forth, or ever you had formed the earth and the world, from everlasting to everlasting you are God." (Psalm 90:2) It is also testified of God in worship, "Holy, holy, holy, is the Lord God Almighty, who was and is and is to come!" (Revelation 4:8)

That is part of the very problem. Mormonism claims to be the most clear and bright beacon of doctrinal clarity, particularly on things that matter. Yet Mormonism's traditional worldview has fostered confusion on the most important thing in all of reality. Mormonism has historically taught, "As man is God once was, as God is man may be." The traditional and majority Mormon view is that while Jesus is unique and special for obtaining godhood in pre-mortality and for living a mortal life sinlessly, Heavenly Father obtained godhood more like we can: he experienced a mortality replete with sin, yet still progressed unto exaltation and godhood. Some Mormon authors essentially appeal to this "one eternal round" as a point of comfort for members. Whether or not the Mormon institution has an official position on the issue, it still bears responsibility for letting such blasphemy persist among members. Individual Mormons still bear responsibility for acquiescing to the institution's lack of repentance over the issue.

They don't have to. What we are talking about here is a natural extension of the traditional Mormon worldview, a worldview that Mormon leaders are responsible for fostering and acquiescing to.

Jesus Christ prayed to the Father, "this is eternal life, that they know you the only true God, and Jesus Christ whom you have sent" (John 17:3). Eternal life is to know God. Do you want to know God? Then it matters.

Unrepentant idolaters go to hell. We learn in Revelation 21:8 that the "cowardly, the faithless, the detestable, as for murderers, the sexually immoral, sorcerers, idolaters, and all liars, their portion will be in the lake that burns with fire and sulfur, which is the second death." In the larger context, this is speaking of post-resurrection eternal hell (not the temporary spirit prison of the intermediate state).

Idolatry is fundamentally exchanging "the truth about God for a lie" (Romans 1:25). Whether you are worshiping a golden calf, Baal, Zeus, the Flying Spaghetti Monster, or a god who was perhaps once a sinner, you are an idolater, because the god you worship is not the God of the Bible.

The whole beauty and power and value of the atonement is based on the fact that it was accomplished by a God who never, ever sinned.

The purpose of life is embedded in the greatest of all commandments: "Hear, O Israel: The Lord our God, the Lord is one. And you shall love the Lord your God with all your heart and with all your soul and with all your mind and with all your strength." (Mark 12:30) All things considered, the purpose of life is to enjoy and fear and worship and love and delight in God, ultimately in the God-given context of human community and creation.

Yes. John testifies by the Holy Spirit, "If we confess our sins, he is faithful and just to forgive us our sins and to cleanse us from all unrighteousness." (1 John 1:9) Start singing "Amazing grace, how sweet the sound, that saved a wretch like me" in your heart with Christians, and repent of believing in a god who could himself be singing it. God was never a wretch like us, but he loves to save wretches like us.

This is the theory that both God the Father and Jesus Christ belong in a special strain of savior gods. There are multiple problems with holding this view: 1) It has the non-biblical assumption that God the Father had to progress over time unto full godhood. 2) It is a private interpretation that your Church has not endorsed. 3) You are (presumably) still unrepentantly committed to a religion which acqueisces to millions of its members believing that God the Father could have been a sinner. 4) If you still hold to the traditional Mormon view that we can become gods over our own worlds and spirit children, then it fellows that your own spirit children would be worshiping you, a being who is not in the special strain of savior gods. So the problem is simply moved from one planet to another. Also of note is Bruce McConkie's thoughts on the issue (as reported by his son):

"KFD 5:1 Jesus, what are you going to do? To lay down my life as my Father did. Joseph Smith's purpose is to show that the Bible teaches that our Father in Heaven was once mortal, as we are. To do so he takes John 5:19 as a text. Here the Savior said, 'The Son can do nothing of himself, but what he seeth the Father do: for what things soever he doeth, these also doeth the Son likewise.' The Prophet then reasons that it is Christ's purpose to lay down his life and take it up again. Thus, if Christ can do only that which his father did, his father must also have been subject to death, he must have died and then taken up his life again as a resurrected being. From this statement of the Prophet, many have attempted to reason that he was saying that his father was also a savior for those of another world and thus that all worlds require their own saviors. The Prophet never taught such a thing and was not alluding to it here. His remarks centered on the doctrine of resurrection, not the salvation of God's endless creations. The Prophet had already clearly taught that the atonement of Christ---which was infinite---embraced all that he had created under the direction of the Father (see commentary on D&C 76:23-24). Responding to those who wanted to argue that there is a special strain of savior gods, Elder Bruce R. McConkie often asked, 'What earthly good could possibly come from teaching such a thing?' " - Joseph Fielding McConkie and Craig J. Ostler, Revelations of the Restoration: A Commentary on the Doctrine & Covenants & Other Modern Revelations

That is certainly not the observation I have made after a decade of actively interacting with Mormons, nor is it the collective observation of evangelicals who do ministry to Mormons. The above video I have done is at the cultural epicenter of Mormonism, Temple Square. I have non-selectively included every video interview clip that I can. Also, consider that you might be falsely assuming something about the beliefs of fellow Mormons that you have never sufficiently tested. Most Mormons never think to probe fellow members on such an issue in a thoughtful way.

Please e-mail me at aaronshaf[at]gmail[dot]com

I recommend utlm.org, irr.org, mrm.org, mormoninfo.org, and carm.org.