The outrageous mistakes that Joseph Smith made, in presuming that he could translate the Bible, were, simply, that the Bible scriptures used from the KJV in the BOM, supposedly the most correct book on the face of the earth, prior to Smith's Inspired Version of the Bible (parts of which are currently annotated in the LDS Bible) grossly contradict Smith's translation of the New Testament. How is it that the BOM does not match the JST? For example, take 1 Nephi 14:6, Matt. 7:6, 3 Nephi 13:25-27, Matt. 6:25-27. Smith should have known that this deception would catch-up with him, but I don't really think he cared, for he lived in a very delusional world. After he wrote the BOM, he couldn't go back and change what he had written when he rendered a bogus translation of the Bible. What sophistry can you come up with to explain away what is clear proof that Smith was a charlatan? Yet, you are quite an expert at sophistry and have made many people believe that what is as black as sin is as white and pure as the driven snow. I am quite curious to hear your explanation for this.Hmm, Joseph Smith the careless deceiver didn't even notice that his changes in the Bible didn't match the changes in the Book of Mormon? Are these difference sufficient for us to expose him as a fraud--and a very inept one at that?
There are some assumptions built into this question. One assumption is that that the Inspired Version is a restoration of original scripture. Did Joseph ever say that? This work was not completed and not canonized, but is treated as a helpful study aid. Many LDS writers examining the work-in-progress that Joseph left us with his "translation" of the Bible see it as containing not just corrections or restorations of material but also added explanatory material that we need not imagine was meant to convey the original words of ancient prophets and apostles, but may help clarify their meaning. In addition to mistakenly assuming the Inspired Version to be a complete, perfect Urtext, a less questionable assumption is that the authors of the Book of Mormon should have been citing the pure text that Joseph restored.
The fact that Joseph wasn't troubled by differences in the Inspired Version and related Book of Mormon passages is not clearcut evidence of totally inept fraud, but should be a clue about what his exercise meant.
So our critic expects us to roll over an reject Joseph because what may be clarifying commentary in his work-in-progress with the Bible wasn't also added to the Book of Mormon (at least not before he was killed). Sure, you can reject Joseph over that, but it's not an impressive argument, in my opinion.
We live in a mortal world where lots of things are imperfect, including the Church and any edition so far of the Book of Mormon. An almost fundamentalist expectation that everything fit together to suit our assumptions and logic can be a quick way toward disappointment. Stepping back and taking a slightly more flexible and open-minded, inquiring approach makes a lot more sense to me.
A related question is on my LDSFAQ page (Mormon Answers) about apparent problems in the Book of Mormon.