First, are the crowd that make up doctrine as they go along. I'll fix that: The "man in the white robe" is an angel:
Second, are the (obviously misguided, based upon their conviction of something very, very wrong) people who are awaiting the "sealed portion of the plates":https://www.lds.org/general-conference/ ... s?lang=eng
"The Ministry of Angels" Jeffrey R. Holland, Oct 2008
From the beginning down through the dispensations, God has used angels as His emissaries in conveying love and concern for His children. Time in this setting does not allow even a cursory examination of the scriptures or our own latter-day history, which are so filled with accounts of angels ministering to those on earth, but it is rich doctrine and rich history indeed.
Usually such beings are not seen. Sometimes they are. But seen or unseen they are always near. Sometimes their assignments are very grand and have significance for the whole world. Sometimes the messages are more private. Occasionally the angelic purpose is to warn. But most often it is to comfort, to provide some form of merciful attention, guidance in difficult times. When in Lehi’s dream he found himself in a frightening place, “a dark and dreary waste,” as he described it, he was met by an angel, “a man … dressed in a white robe; … he spake unto me,” Lehi said, “and bade me follow him.”7 [ 1 Nephi 8:7, 5–6.] Lehi did follow him to safety and ultimately to the path of salvation.
Quote me here, now, that if someone is rejecting God's messengers, or not receiving the light given to them already, they'll never get anymore. Besides, there's nothing new or novel to be gained that wouldn't already be gained by following precepts you already have. The sealed portion Prophets (and subsequently their messages), only comes by following line, upon line. And it ALL comes, line upon line. (Or as Neal A. Maxwell said, the successive use of stepping stones). No amount of sealed writings will miraculously advance someone from learning line upon line, and nothing can stop a person who is learning, line upon line, from receiving the entire truth, in time.
Third, are the people who, rather than listen to the prophets, "reason among themselves" (as the Savior termed). The "strain at a gnat, swallow a camel" crowd. This is why there are so many people that I have learned aren't in any position to expound, upon the church, upon the Lord, or upon scripture. Given to themselves, they turn angels into devils.
Oh brother. Speaking of brothers, I wonder how many people spouting false doctrine--and teachings-- could have this same problem solved, if, instead of being like Laman and Lemuel, they merely inquired of the Lord. They, after all, were unable to comprehend the dream either. They're in good company.
And lastly, to answer the original poster, the man in the white robe is an angel, sent from God. Lehi was [led] to the path of salvation by him. The mists of darkness are temptations. They come regardless if you are a prophet, the Savior of the world, or an armchair internet prophet. The angel didn't cause Lehi to be lost, he was (metaphorically) lost due to temptation.
Here's what Orson Pratt had to say (some people love dead prophets, and reject living ones):
There should be little confusion now, now go forth, and teach CORRECT doctrine!Spirit of Light and Truth—Its Value—Its Opposite Necessary—Final Triumph of Light and Truth.
Discourse by Elder Orson Pratt, delivered in the 13th Ward Assembly Rooms, Nov. 24, 1872.
Reported By: David W. Evans.
But now having spoken so much about the benefits of this light, and how good it would be to be continually guided and instructed by the spirit of revelation, there is another thing connected with it which we perhaps do not all fully understand. Supposing a person were thus guided all the time, from waking in the morning until they retired to rest at night; and then when asleep if his dreams were given by the same spirit, and this should be the uninterrupted condition of an individual, I ask, where would be his trials? This would lead us to ask, Is it not absolutely necessary that God should in some measure, withhold even from those who walk before him in purity and integrity, a portion of his Spirit, that they may prove to themselves, their families and neighbors, and to the heavens whether they are full of integrity even in times when they have not so much of the Spirit to guide and influence them? I think that this is really necessary, consequently I do not know that we have any reason to complain of the darkness which occasionally hovers over the mind. I recollect that Lehi had a very great and important dream communicated to him, and his son Nephi had the same renewed to him. While Lehi was on his way to this country he dreamed that he wandered many hours in darkness; that there was a certain rod of iron, notwithstanding this darkness that seemed to gather around him, on which the old man leaned steadfastly. So great was the darkness that he was fearful he should lose his way if he let go the rod of iron; but he clung to it, and continued to wander on until, by and by, he was brought out into a large and spacious field, and he also was brought out to a place where it was lighter, and he saw a certain tree which bore very precious fruit. And he went forth and partook of the fruit of this tree, which was the most precious and desirable of any fruit that he had ever tasted; and it seemed to enlighten him and fill him with joy and happiness. Lehi was a good old man—a man who had been raised up as a great prophet in the midst of Jerusalem. He had prophesied in the midst of all that wickedness which surrounded the Jews; and they sought to take away his life, because of his prophecy. But notwithstanding this gift of prophecy, and the gifts of the Spirit which he enjoyed, the Lord showed him by this dream that there would be seasons of darkness through which he would have to pass, and that even then there was a guide. If he did not all the time have the Spirit of God upon him to any great extent, there was the word of God, represented by an iron rod, to guide him; and if he would hold fast to that in his hours of darkness and trial, when everything seemed to go against him, and not sever himself therefrom, it would finally bring him where he could partake of the fruit of the precious tree—the Tree of Life.