Mormons like to parade Joseph Smith's perfections about as testament to his prophetic glory. An unschooled farm boy raised in poverty, they say, must have enjoyed uncommon heavenly help to learn the scriptures as he did, learn to write as he did, and so on. Though these claimed demonstrations of divine approval probably don't miss the mark by much, they also don't prove Joseph Smith was a prophet, and they gloss over Joseph's flaws. "Anti-Mormons" on the other hand, or more generally those who would dismiss Joseph Smith as a fraud, focus on his mistakes, or in any case on stuff that appears to our modern eyes as foolish, misguided, or downright sinful. Plural marriage in its different forms springs immediately to mind, as does his adherence to folk magic, his translation of the Kinderhook plates (and, for that matter, of the Book of Abraham), and so on. The Doctrine and Covenants itself provides examples of Joseph Smith's shortcomings; as early as section 3, the Lord commands him to repent and describes in some detail the nature of Joseph's mistakes.
And therein lies the key to the matter: a prophet is no more perfect than any of the rest of us, no matter how exultantly we proclaim the praises of whichever mortals we currently call prophets, and no matter how disastrously they prove their fallibility. Moses, for example, messed up badly enough he wasn't allowed to enter the land he'd led his people toward for forty years. Yet apparently the Lord approved of him anyway, because he was assigned to appear on the Mount of Transfiguration. The Lord is far more ready to forgive and comfort us than we are often willing to accept. For instance, the Missouri saints were driven out of their homes and suffered terrible hardships not, as we love to believe, because of religiously intolerant neighbors and wanton frontier violence, but because of their "jarrings, and contentions, and envyings, and strifes, and lustful and covetous desires" (D&C 101:6) Because of those sins, many were killed and all were forced to leave their belongings and run, and yet the Lord was still willing not just to forgive but to save them, comfort them, crown them, and make them His jewels (v. 3, 9-15).
It will never do to dismiss Joseph Smith as a prophet simply because of his imperfections. When the Lord says He gives men weakness that they may be humble (Ether 12:27) He doesn't somehow exempt the prophets. Anti-Smith claims simply tell us what we already knew -- that he was human. This should not discourage us from studying his teachings; it should teach us that if a mortal, flawed much like we are ourselves, can gain God's favor, so can we. "God hath not revealed anything to Joseph, but what he will make known unto the Twelve, and even the least Saint may know all things as fast as he is able to bear them." (Discourses of the Prophet Joseph Smith) That is comfortable and beautiful doctrine.
And therein lies the key to the matter: a prophet is no more perfect than any of the rest of us, no matter how exultantly we proclaim the praises of whichever mortals we currently call prophets, and no matter how disastrously they prove their fallibility. Moses, for example, messed up badly enough he wasn't allowed to enter the land he'd led his people toward for forty years. Yet apparently the Lord approved of him anyway, because he was assigned to appear on the Mount of Transfiguration. The Lord is far more ready to forgive and comfort us than we are often willing to accept. For instance, the Missouri saints were driven out of their homes and suffered terrible hardships not, as we love to believe, because of religiously intolerant neighbors and wanton frontier violence, but because of their "jarrings, and contentions, and envyings, and strifes, and lustful and covetous desires" (D&C 101:6) Because of those sins, many were killed and all were forced to leave their belongings and run, and yet the Lord was still willing not just to forgive but to save them, comfort them, crown them, and make them His jewels (v. 3, 9-15).
It will never do to dismiss Joseph Smith as a prophet simply because of his imperfections. When the Lord says He gives men weakness that they may be humble (Ether 12:27) He doesn't somehow exempt the prophets. Anti-Smith claims simply tell us what we already knew -- that he was human. This should not discourage us from studying his teachings; it should teach us that if a mortal, flawed much like we are ourselves, can gain God's favor, so can we. "God hath not revealed anything to Joseph, but what he will make known unto the Twelve, and even the least Saint may know all things as fast as he is able to bear them." (Discourses of the Prophet Joseph Smith) That is comfortable and beautiful doctrine.