Many traditional Christians envision Peter standing at the "pearly gates." They are uncomfortable with the misunderstanding that Brigham Young said Joseph Smith will take Peter's place. The thoughtful reader, however, will search the entire discourse delivered by Brigham Young and see that this is not what he was teaching.
Each dispensation has a prophet at its head. Moses taught in his dispensation that those who looked to the serpent on a pole would live. This was a type (Alma 33:19) or similitude of the Savior. Those who didn't obey Moses and would not look, didn't live. Accepting what Moses said in that dispensation was the "passport" to life.
As Christ said:
Do not think that I will accuse you to the Father: there is one that accuseth you, even Moses, in whom ye trust.If they didn't believe in Moses, he wasn't their "passport."
For had ye believed Moses, ye would have believed me: for he wrote of me.
But if ye believe not his writings, how shall ye believe my words? (John 5:45-47)
Noah offered "salvation" to those who would join him in the ark. Those who were disobedient and failed to enter the ark were swept off the earth in the flood and ended up in spirit prison (1 Peter 3:20). Again, as the prophet of his dispensation, Noah provided the "passport" for those who accepted the word of God that came through him.
In the meridian of time, those who accepted the apostles and prophets and did not reject the message of Jesus Christ were saved. As the Lord said to the apostles, "He that receiveth you receiveth me" (Matt. 10:40).
While speaking about our own dispensation, Brigham Young said that people of this dispensation will not enter God's Kingdom without the "consent" and "certificate" of Joseph Smith as a passport to entering where God and Christ are. Brigham Young then explained what he meant: "It is his [Joseph's] mission to see that all the children of men in this last dispensation are saved, that can be, through the redemption" (Journal of Discourses, vol.7, p.289).
The "passport," then, that people will need to enter heaven is the same as they have always needed, no matter what dispensation they lived in. To accept Christ is to accept his prophets: without the priesthood authority and inspired teachings of the Lord that have come through Joseph Smith, no one in this dispensation, living or dead, can be redeemed.
Anti-Mormon critics distort this view, trying to make it appear that Joseph Smith will be standing by the gate of heaven admitting or rejecting those who seek to enter. This is not the picture that is painted by Brigham Young. He was merely stating that the mission of Joseph Smith, God's prophet, was "to see that all the children of men in the last dispensation are saved, that can be through the redemption."
It should be recognized that the Savior is a great delegator. He has delegated to the "head" of each dispensation certain responsibilities, including some preliminary judging responsibilities. For example, in New Testament times the Apostles were told that they will judge the twelve tribes of Israel (Matt 19:28). Literally, then, those of the Twelve Tribes won't "get to Heaven" without the consent of the Apostles.
Latter-day Saints do not believe Joseph Smith is the keeper of the gate of heaven, nor the one who determines whether we are saved. Some Christians think they will instead meet Peter at the "pearly gates," but The Book of Mormon teaches who will really be the final "gatekeeper":
O then, my beloved brethren, come unto the Lord, the Holy One. Remember that his paths are righteous. Behold, the way for man is narrow, but it lieth in a straight course before him, and the keeper of the gate is the Holy One of Israel; and he employeth no servant there; and there is none other way save it be by the gate; for he cannot be deceived, for the Lord God is his name (2 Nephi 9:41).