I was going to comment (if comments weren't disabled for what are probably excellent reasons) that an even better analogy might be the number of evangelicals who are aware of the controversies over the authorship of certain Pauline epistles.
Outside of those who interact with Biblical scholarship, most evangelicals I doubt are aware that the authorship of several of Paul's epistles is hotly contested, and it's a given, even among many conservative scholars, that he didn't write the Pastorals.
I guess that I did not think of that analogy because I am skeptical of some of the arguments on the authorship of Paul's epistles. It also seems to me that Paul's epistles are much more central to Evangelical thought than the Joseph Smith Papyri are to Latter-day Saint thought. On the other hand, I cannot recall the last time I have seen the book of Nahum cited in evangelical literature. I know that evangelicals have written commentaries on it and I would not be surprised if I agreed with much that they might have to say on the subject, but Nahum does not seem to be on most Evangelical's radar screens. The same could be said of Habakkuk. The Joseph Smith Papyri are probably of less importance to most Latter-day Saints than the book of Nahum is to most Evangelicals because Latter-day Saints do not think of the Joseph Smith Papyri as being "God-breathed" the way that Evangelicals think of anything in the Bible (which presumably includes Nahum) as being "God-breathed."Is the evangelical movement not true because most evangelicals have a mistaken view of the historical background of Ephesians or 2 Thessalonians?
It seems to me that one of the problems that appears in dialogues between Evangelicals and members of the Church of Jesus Christ is that Evangelicals have a view of scripture that does not allow for any mistakes or errors. They view scripture as "God-breathed" and perfect. Members of the Church of Jesus Christ, however, do not think that their scriptures are perfect. The Book of Mormon tells them that there are errors in the Bible and that the Book of Mormon is not perfect, and that neither is complete. Thus some Evangelicals think that if they can find even one error in the scriptures of the Church of Jesus Christ, that that error invalidates the entire scripture and the entire Church. We simply do not see it that way.