Joseph Smith was a con man
The authenticity of the Book of Mormon depends on the credibility of Joseph Smith, the supposed translator of the book. However, he admitted to perpetrating various gold digging, divining and necromancy activities.  Most accounts describe Joseph Smith actually testifying under oath that he really could divine the location of treasure! If he thought he could divine treasure with a seer stone, he was self-deluded; if it was knowingly deceiving people, he was a con man. Joseph Smith used the same seer stone as one aids to his "translation" of the Book of Mormon. 
Joseph Smith also produced an erroneous translation of several Egyptian papyrus scrolls to produce the "Book of Abraham".
1826 Bainbridge Trial
There are several accounts of Joseph Smith's trial in which he was accused of attempting to divine for treasure and charging fees for his fraudulent services.
- "[Smith testified] he had a certain stone which he had occasionally looked at to determine where hidden treasures in the bowels of the earth were; that he professed to tell in this manner where gold mines were a distance under ground, and had looked for Mr. Stowel several times, and had informed him where he could find these treasures, and Mr. Stowel had been engaged in digging for them. That at Palmyra he pretended to tell by looking at this stone where coined money was buried in Pennsylvania, and while at Palmyra had frequently ascertained in that way where lost property was of various kinds; that he had occasionally been in the habit of looking through this stone to find lost property for three years, but of late had pretty much given it up on account of its injuring his health, especially his eyes, making them sore; that he did not solicit business of this kind, and had always rather declined having anything to do with this business. [...] And therefore the Court find the Defendant guilty. Costs: Warrant, 19c. Complaint upon oath, 25 1/2c. Seven witnesses, 87 1/2c. Recognisances, 25c. Mittimus, 19c. Recognisances of witnesses, 75c. Subpoena, 18c. - $2.68. "
- "[Smith testified] With some labor and exertion he found the stone, carried it to the creek, washed and wiped it dry, sat down on the bank, placed it in his hat, and discovered that time, place and distance were annihilated; that all intervening obstacles were removed, and that he possessed one of the attributes of Deity, an All-Seeing-Eye. [...] the prisoner was discharged, and in a few weeks left the town. "
- "For several years preceding the appearance of his book, [Joseph Smith] was about the country in the character of a glass-looker: pretending, by means of a certain stone, or glass, which he put in a hat, to be able to discover lost goods, hidden treasures, mines of gold and silver, &c. Although he constantly failed in his pretensions, still he had his dupes who put implicit confidence in all his words. In this town, a wealthy farmer, named Josiah Stowell, together with others, spent large sums of money in digging for hidden money, which this Smith pretended he could see, and told them where to dig; but they never found their treasure. [... Smith was] arrested as a disorderly person, tried and condemned before a court of Justice. But, considering his youth, (he being then a minor,) and thinking he might reform his conduct, he was designedly allowed to escape."
The main ambiguity in the accounts is the verdict and sentence. However, all accounts consider Smith to be a diviner (self confessed or not). If Smith was using the same seer stone to translate the plates that he previously admitted in court to having used for nefarious money-digging and scams, then God apparently approved of those activities. In fact, if God led Joseph to find the seer stone, then God is complicit in the bilking money from Smith's neighbors.
- "From the point of view of Mormon history, it is immaterial what the finding of the court was on the technical charge of being 'a disorderly person and an imposter'; what is important is the evidence adduced, and its bearing on the life of Joseph Smith before he announced his claim to be a prophet of God. "
Since the key religious text of Mormonism is a forgery, the entire belief system disintegrates.
Some apologists claim that Smith's confession is a forgery.
Others simply restate that Joseph Smith really did have the power of divination.  In 2015, the church released photographs of a stone in its possession that was used in the production of the Book of Mormon.  If they want to provide evidence of their validity, they would demonstrate they still work (under scientifically controlled conditions). The James Randi Educational Foundation would be happy to help them organize a suitable demonstration (and pay a large prize if they are successful). However, the church will not do this because divination is a fraud. Joseph Smith had mixed success with personal finances, which is not what one would expect if someone really could divine for buried treasure!
Smith was prosecuted many times on related charges which bring his honesty into question, including:
- Disorderly person, June 1830 (acquitted)
- Illegal banking, February 1837 (jumped bail, found guilty in absentia)
- Conspiracy to murder Newell, June 1837 (dismissed)
- Banking fraud, 1838 (fled arrest)
- Threats to Judge Adam Black, August 1838 (jumped bail)
- Missouri treason case, November 1838–39 (escape custody and fled)
- Arrest for fleeing Missouri, 1841 (released)
- Conspiracy to murder Governor Boggs, 1842–43 (released)
- Missouri treason case, June 1843 (dismissed)
- Perjury, fornication and polygamy, May 1844 (murdered while awaiting trial)
- Inciting a riot destroying the Nauvoo Expositor, June 1844 (murdered while awaiting trial)
- Treason against Illinois, June 1844 (murdered while awaiting trial)
Isn't this just ad hominem?
An interesting objection to this argument is that critics of Joseph Smith are using ad hominem attacks.
- "Claims that Joseph was a "juggler," or "conjurer" were a common 19th century method of dismissing his prophetic claims via ad hominem. Modern-day claims about him being found to be a "con man" are simply the same attack with updated language "
If Joseph Smith was advancing a well argued case using reason and evidence, then it would be inappropriate for critics to bring Smith's character into question. They should simply address his argument since anything else would be a red herring.
However, Smith is not attempting to use logical argument but instead reporting divine revelation. In that case, the question of his trustworthiness is very relevant and an ad hominem is actually not fallacious in this context. In a sense, Joseph Smith uses an argument from authority (in this case his own authority) to authenticate the Book of Mormon. For skeptics, the word of a con man or self proclaimed diviner does not amount to much.
- ↑ Christopher Hitchens, Mormonism: A Racket Becomes a Religion, 2011
- ↑ 
- ↑ Fraser's Magazine, February, 1873, vol. VII, p. 229-230 
- ↑ W. D. Purple., Joseph Smith The Originator of Mormonism, Greene, April 28, 1877.
- ↑ A. W. Benton, Mormonites, Evangelical Magazine and Gospel Advocate, Utica, N.Y., April 9, 1831.
- ↑ John Philip Walker, ed., Dale Morgan on Early Mormonism: Correspondence and a New History (Salt Lake City: Signature Books, 1986), 373, n. 44.
- ↑ 
- ↑ Revealed: the stone that 'translated' the Book of Mormon
- ↑