I'm hardly an expert on the Book of Mormon, but this quote surprised me so I googled it. It appears to be an accurate quote but is not fully attributed. As best I can make out, the speaker is the antichrist (or some such evil character; not sure on the exact mythology in play here).
Failure to note that means this quote gives either an incorrect view of the Book of Mormon, or of the significance of the text, or both.
When quoting fiction, I recommend identifying both the character and the author. E.g.
Ye say that those ancient prophecies are true. Behold, I say that ye do not know that they are true.
--Korihor in the The Book of Mormon (Alma 30.24-28); Joseph Smith, 1830
Having said all that, it's still a damn good rationality quote.
I would think it's bad publicity for us to explicitly note a resemblance to antichrist-type characters.
Another month has passed and here is a new rationality quotes thread. The usual rules are: