I am only giving you the Mormon prospective. So for us, ignoring JS would be similar to you ignoring Peter, the apostle of Jesus, and what he taught.
I know that, Peter. I'm just pointing out that this is not an argument itself -- it's stating a belief, without any backing as to why it is as it is (i.e., how and why is JS to be considered as we consider St. Peter?). Mormons may accept JS as a prophet akin to St. Peter, but nothing in simply stating that tells anyone why they should have to do the same. So it seems like you're taking your conclusion as though it should be obvious to everyone, even though it isn't. And since it isn't, things like the premise of the OP strike the non-Mormon as nonsensical at best.
Even as a young person, when I read the 76th section of the D&C, it made sense to me that God cannot limit His judgement to just good and bad. The good go to heaven, and the bad go to hell. There are too many variations of good and too many variations of bad.
For instance if you are 51% to 100% good, you go to heaven. And if you are 49% to 1% good you go to hell.
Think about what heaven will be like. You have everyone from being 51% good to 100% good. Are those that are 51% good going to be comfortable around those that are 100% good? The answer is no. And that is the reason for the many mansions concept. It is not a cookie-cutter deal, 1 size fits all.
In hell, is it fair to put those who were 49% good with those that are 1% good? Are those that are 49% good going to be comfortable with those that are 1% good? No again.
God will be the judge and He will have the ability to see into our hearts and will place us where we will be comfortable for eternity. Some will be close to Him, some will be a short distance away from Him, some will be a long distance away from Him. It depends on your righteousness and your good works, as we will be judged according to our works. The separation into kingdoms will be along those lines.
What is objectionable in all this is not the idea that there is a difference in reward according to each person, as that is in the scriptures themselves (recall, e.g., the parable of the talents) and all over the Fathers, but the actual schema that originates in Mormonism and is found only in Mormonism.
You know, this thing:
That is found nowhere in any Christian tradition. What is found are things like the following, from St. Jerome's
Against the Pelagians (written 417):
In a great house there are different vessels, some of gold, some of silver, brass, iron, wood. And yet while in its kind a vessel of brass is perfect, in comparison with one of silver it is called imperfect, and again one of silver, compared with one of gold, is inferior. And thus, when compared with one another, all things are imperfect and perfect. In a field of good soil, and from one sowing, there springs a crop thirty-fold, sixty-fold, or a hundred-fold. The very numbers show that there is disparity in the parts of the produce, and yet in its own kind each is perfect. Elizabeth and Zacharias, whom you adduce and with whom you cover yourself as with an impenetrable shield, may teach us how far they are beneath the holiness of blessed Mary, the Lord's Mother, who, conscious that God was dwelling in her, proclaims without reserve, "Behold, from henceforth all generations shall call me blessed. For He that is mighty hath done to me great things; and holy is His name. And His mercy is unto generations and generations of them that fear Him: He hath showed strength with His arm." Where, observe, she says she is blessed not by her own merit and virtue, but by the mercy of God dwelling in her. And John himself, a greater than whom has not arisen among the sons of men, is better than his parents. For not only does our Lord compare him with men, but with angels also. And yet he, who was greater on earth than all other men, is said to be less than the least in the kingdom of heaven.
So we are to avoid talking as though there is no distinction to be made, because there absolutely is. But note that what is lacking here is the Mormon neo-Gnostic and at least semi-Pelagian idea that you go to this or that particular place or state relative to your own works. (Pelagius, by the way, believed that people could earn their salvation by basically choosing to behave right, without the aid of the divine grace of God in all cases; if you read the
wikipedia article on Pelagianism, you will find that it is an idea that has been embraced by some Mormon scholars as being
de facto consistent with Mormon theology.)
From the Christian view, the Mormon schema is the codification of speculation on matters that have most definitely not been revealed to us (and is generally taken to be an allegory anyway, as in Dante; you'll note how St. Jerome above likens it to this or that -- he does not say "You
literally go here if you do or don't do XYZ"; as Christ also spoke in parables, I think this is safely within what is reasonable to do, unless of course you want to seriously make the case that Jesus Christ our God meant
literal mansions, as in buildings of stone, which I don't think is supportable at all). Maybe the Mormon would claim that they have been revealed to JS or some other Mormon prophet, and therefore are to be believed on that account, but then we're back to why should anyone else take that seriously when the weight of Christian history of all traditions is against the codification of such speculation as in the Mormon case (and, I would say as an Orthodox person, as in the Roman Catholic case with regard to purgatory and formerly limbo; so it's not as though such things are absent from Christianity, either, though I would personally say they are equally unwise for essentially the same reasons).
