Mosiah 4:8 "And this is the means whereby salvation cometh. And there is none other salvation save this which hath been spoken of; neither are there any conditions whereby man can be saved except the conditions which I have told you."
This is an interesting statement, and a bold proclamation, especially in our day. Our nation, the United States tries to be so PC about every belief system, and it has created this pernicious doctrine that everybody is right, and nobody is wrong, and that is the work of Satan. Because, if everybody is right, and every religion is correct, then what does it matter what religion you join.
This thought process trivializes religion. Religion becomes a lifestyle choice, dependent on factors that have nothing to do with God. There is no search for truth, because the truth is in front of you, in whatever form you accept it.
This search for truth is what separated Joseph Smith from so many others. While most people were seeking the church they liked the best, or fit with their way of thinking best, Joseph Smith wanted to know the untainted truth, not what he wanted to hear, but what God wanted him to hear.
D&C 93:30 tells us that “all truth is independent in that sphere in which God has placed it”, this statement means that truth is independent of our beliefs, and knowledge, or lack thereof. Truth is truth, and cannot be changed. The truth does not change, just our understanding about the truth.
Just as Ammon stated, “there is none other salvation save this which hath been spoken of”, we need to be telling the world that there is no other true church upon the Earth, and no other true doctrine.
If every church is right, then every doctrine in every church is correct. If every doctrine in every church is correct, then God is changeable to interpretation. If God is changeable, then he is not God, for God is unchangeable. And if there be no God, then no church is correct, because all churches teach of God in a different way. If no church is correct then we are, as Paul said, “Of all men most miserable.” (1 Cor 15:19)