Sources of Scripture in Mormonism

This is an important thing to consider when perusing anti-mormon literature. You would think, given several books and thousands of speeches by the Prophets, that detractors of the Mormon Church would have plenty of ammo. But very often they cite sources that are not official proclamations of the Church. One fun example is that Brigham Young prophesied that man would never land on the moon. Young did, in fact, say this, but not in the role of a prophet. I believe he was conducting an informal interview or something. Other examples are citing information from Church newspapers, magazines, pamphlets, etc. The members of the Church are completely capable of totally screwing up the teachings of the Church. Mormons don't consider the Prophet to be above-human either, and he can make mistakes and say incorrect things in his daily life.

Besides the Catholic Church, I'm not sure of too many other religions that have so much information available with so little contradictions.

It's worth noting that the Church has made statements that other books, like the Book of Mormon may be released in the future. The Book of Mormon itself is an abridgement of a much larger collection of writings by ancient Prophets. The catch is that this won't happen until the members of the Church start fully utilizing what they already have.

For every quote by a Mormon attempting to excuse the words of a prophet by insisting he wasn't acting as a prophet at the time he said something, there is always another Mormon ready to state that we need to follow every word that comes from a prophet's mouth. There is a good amount of muddlement on this issue, and in practice most Mormons end up not even researching the disturbing things like this that Brigham Young or other old prophets have said, since "a living prophet trumps a dead one", and it's easier not to deal with disturbing issues.

"Anti-mormons" actually do have a lot of "ammo" to bring against the LDS church, especially on scriptural sources (see Book of Abraham and Book of Mormon). It's just that most Mormons refuse to consider much ammo to be real ammo and are adept at providing excuses for issues they find troubling.