When Alma taught the people of Ammonihah, they reacted as follows:
4 And they said also: We will not believe thy words if thou shouldst prophesy that this great city should be destroyed in one day.
5 Now they knew not that God could do such marvelous works, for they were a hard-hearted and a stiffnecked people
A lot of people take this approach to God's servants - "I will believe unless the prophet says this." In the recent election in California, when proposition 8 caused such great division among the citizens, the first Presidency and the Quorum and of the Twelve Apostles told the saints that redefining marriage would harm our society and was contrary to the will of the Lord. They encouraged church members to be actively involved in campaigning for proposition 8 by joining groups supporting the proposition, by contributing money, and by voting for it. There were some members who said, "The Church has no business being involved in a political question or in telling members how to vote." They said, in effect, "We will not believe thy words if thou shouldst tell us to support proposition 8." Some seethed with anger and even left the church.
The Lord said of the Prophet of God (D&C 21),
4 Wherefore, meaning the church, thou shalt give heed unto all his words and commandments which he shall give unto you as he receiveth them, walking in all holiness before me;
5 For his word ye shall receive, as if from mine own mouth, in all patience and faith.
We are on treacherous ground when we make ourselves the arbiters of truth and choose to ignore the teachings of the living prophets and apostles. If we have a question about some teaching or directions given by the brethren, we should ask the Lord in prayer to help us understand and know for ourselves that it is His will.