One of the interesting things about Moby Dick is that there are no heroes. The most sympathetic characters are Ishmael and the Harpooners (a great band name), but they are all passive observers in the story, literally tossed about by weather and maelstrom. Then there is Starbuck, the nice guy, whose inability to ultimately stand up for what he believes makes him an innocent bystander in his own death. Starbuck's death (and the sinking of the Pequod) barely register as we wrestle our way through the final chapter.
The most compelling two characters are Ahab and Moby Dick. Let's just call the whale evil or chaos and leave it at that. We don't have to give it human motivations in order to make the story comprehensible, so we don't bother. Slap a label on the whale (hopefully, it won't anger him) and move on.
Ahab, however, denies easy labeling. His motivation, like all great passions, is interesting to us. We are entertained and, sometimes, inspired by people who diligently and determinedly follow their dreams, even if their dreams are somewhat lacking morally (I really must have my revenge on that whale).
Ahab is held up for most of the book as an example of imminent competence. He seems entirely capable of killing that whale and we may even be surprised that he didn't manage it the first time. We may not even get this impression from Ahab himself (if I recall correctly, Ahab isn't around that much on deck), but we get the impression from the men whom he has chosen and the efficient, skilled manner in which they go about their work. There is never any doubt about who will win in the cetacean/sapien contest until we approach the end of the book.
Moby Dick is a force, but not one to be reckoned with. At the appearance of the White Whale the appropriate response seems to genuinely be flight. Like the great epics of early civilizations, the deep is a source of life, but it is also a chaotic, destructive force that is beyond human comprehension. In both Job and Genesis, whales appear as examples of God's creative power, because these are things to which it is futile to compare humans. We're not even on the same scale. The existence of whales is used to acknowledge that some things are simply beyond us.
But Ahab will not understand this. The rational captain may understand it. The whale is too deadly. One could live a long, profitable life with that pretty wife left back in Nantucket if one simply gave up on that whale. But Ahab will not. There is nothing in life that can defeat Ahab and he is determined to prove it. He must have his revenge; he must kill this whale or his life will have been useless, meaningless. Like Harry Potter and Voldemort, if one lives the other cannot (at least, that is how Ahab sees it).
Why must we tackle the whales ourselves? Jacob, in 2nd Nephi 9:19, compares death and hell (meaning physical and spiritual death) to monsters. Dan Belnap (whom you don't know, but I do) has pointed out that Death and Hell are monsters associated with the sea in the Ugaritic Baal cycle. Baal, like Ahab, sets out to defeat the monsters and, like Ahab, he is killed. The truth is that there are some monsters that simply are beyond our power to defeat. We find most of these monsters in ourselves (as self-destructive behaviors, favorite sins, etc.).
Baal was brought back from the monster, Death, by the intervention of divine mediation (his sister and his mother fought for his release). Ahab is a bit different because he ultimately refuses the help of others. He must put the harpoon in Moby Dick himself. He will have no intermediary, he must conquer, must control the situation himself or it will have been fruitless for him.
I think that everyone at some point finds themselves facing that whale. Are we willing to do what we must to defeat it (ie. getting outside help) or are we so stuck on ourselves that we make our defeat certain by assuming the certainty of our success? I believe that it is possible to make the wrong decision here (heck, I do it all the time), but I keep attempting to make the right decision, too. Ahab, seeing the right decision as weak, as belittling, refuses it. It is so important that he kill the whale himself, that he kills himself on the whale.
The point of no return is a state of mind. As long as we steadfastly refuse God, we are there. The vast majority of people will reach this point in their life (there only being one exception, I believe). Most people will understand the futility of the position and back down from this unrealistic, self-destructive, "morally superior" stance, repenting their way back to God. But then there is Ahab. It is within the realm of conceptual possibility that some won't, so the possibility must be considered. Ultimately, will God make us do something that we don't want to do? Can he? Apparently not.
Everyone dies spiritually (if we understand it to mean separation from God). Even Christ did. Those who refuse to live again spiritually will not be forced to. It seems to go against the nature of our relationship to God. However, it seems to me that the vast majority of the people of the earth will realize the futility of jousting with the whale themselves and will come to a welcoming, loving, whale-obliterating Father for help and I thank God for that.