Since you quoted the D&C on this topic, let me give you one more to chew on...
D&C 123:2 For there are many yet on the earth among all sects, parties, and denominations, who are blinded by the subtle craftiness of men, whereby they lie in wait to deceive, and who are only kept from the truth because they know not where to find it—
Okay, again, we can agree just based upon the parable of the wheat and the tares along w/Matt 25:1-10 that there's going to be folks in perhaps most churches who think they are heaven-bound, and there's a surprise waiting them. So the first part of that D&C statement I don't have heartburn with...but then to go on and claim that "they lie in wait to deceive" is simply one of Joseph's "clear the deck" phrases...throw enough mud at every church member of 1830 America and the rest of the world, and you're bound to hit some folks...but sorely miss most.
Listen, why didn't you just go to that BoM passage where Joe says there's only two churches...Christ's church and then the devil's church.
Tell you what. Why don't you have the "Elect Mitt Committee" do a TV ad where he cites this verse. He could say: "I believe in the Book of Mormon. For example...[cits verse]. My church is the Church of Jesus Christ. If you don't belong to it, guess who you belong to?"