I was recently telling a friend about how on my mission I (sort of) knowingly lied to people all the time about the LDS church. I told people that if they got a testimony that the Book of Mormon was true/the word of God, then they would know that the LDS church is true, too. While I believed (and still believe) both those things, I recognized even then that the latter doesn't automatically follow from the former; the Book of Mormon's veracity alone could just as plausibly fit with the view that the Community of Christ (once known as the Reorganized LDS Church) is true, or that the FLDS church is true, or lots of other things. But I didn't spell that out for any of my investigators. Some people might be mad at me for lying to convert people to my religion, but I didn't and still don't have a problem with it. Here's why.
Essentially, what I did was leave out a caveat: that there are other possible inferences to draw from a testimony of the Book of Mormon. The Book of Mormon being true does make it more likely that the LDS church is true, and it is a necessary condition of the LDS church being true. But I didn't spell out every step in my argument, and I didn't define every term precisely at the outset. I was presenting a concise version of (what I took--and take--to be) the truth. I admit, it's inherently paternalistic. But the thing is, it's also necessary. I challenge you to make any argument without leaving anything out. It can't be done. Every story we tell, every argument we make, every truth claim we assert--they're all partial and selective, based on certain assumptions and concealing certain necessary steps. (Lewis Carroll demonstrated this principle beautifully in the field of logic with his short story What the Tortoise Said to Achilles -- text and wiki summary.)
Of course, that doesn't mean you can just leave out enormous steps in any argument and consider yourself justified--if I told you that my gas station had the lowest prices of any place anywhere nearby, but I was defining "anywhere nearby" to mean "within 10 feet of my station," that's grossly misleading and not OK. But my point is that any words we use to express ourselves lie somewhere on the spectrum of misleading--the deception may be inconsequential or it may be significant, but some amount of it is inevitable. I view my statement about the Book of Mormon proving the LDS church's veracity as sitting much more towards the former, innocuous end of the spectrum. Of course, what one considers a minor or major deception depends on a lot of things and is ultimately a value judgment; personally, I feel good about still testifying that the Book of Mormon's truthfulness is one of the proofs that the LDS church is true. Maybe you disagree and think the deception inherent in that claim is unacceptably large, and that's OK. Anyway, I don't think anyone relied purely on a testimony of the Book of Mormon and nothing else when they joined the church--if there isn't a spiritual testimony of other aspects that are actually unique to the LDS church I don't think people will choose to convert.
This issue comes to mind for me all the time now after a few years of law school. Law is in many ways an exercise in trying to pin down words into one specific meaning, which is why contracts are so long and detailed, and why I personally have started getting into the bad habit of using caveats with everything I say. It comes from a good place--I want to minimize the deception I wreak!--but as a byproduct it can increase my annoyance factor and even impede actual communication when I'm in an informal (read: almost every) situation. I'm trying to talk (and write!) using fewer caveats and nuances. It helps me remember when they're actually important and when I need to let the human condition, with all its inherent foibles and shortcomings, just be.