Mormon missionaries, while they no doubt sincerely believe they are doing the Lord's work, are emissaries of Satan, as it is Satan who whispers into the ears of religious con artists like Joseph Smith and their progeny in various latter-day cults.
And, I'd add, we ought to understand this as tragedy; well meaning people who are under a harsh spiritual delusion.
I don't know if this is appropriate here, but I wanted to share my personal experience with Mormon missionaries. It was a long time ago, over 20 years ago in fact. I was in a place where I was still in an early stage of learning about my own Christian faith, having begun to question some of the assumptions of the form of Christianity I had been raised with, and as a result had been engaged in a lot of intense study about the early Church, learning a lot more about Scripture--reading the Bible a lot more than I previously had, and had begun reading some of the works of the early fathers of the Church.
At this time a couple of missionaries came, and I made a decision to let them come in. My goal wasn't to engage in a debate of competing apologetics, rather I was more interested in listening and hearing Mormon beliefs directly from the source, from active and practicing Mormons themselves. It was curiosity, there was what I had been told Mormons believe; but there were a lot of things I had been told certain groups of people believed and I learned that this wasn't always accurate, so I wanted to hear things from Mormons themselves.
What transpired was a largely, and clearly obvious, routine script; and whenever I had questions it seemed like I was interrupting them. Almost as though they didn't fully expect to get asked anything, and they even admitted that they didn't really know how to answer many of my questions, but that they'd bring a more knowledeable guy with them next time if they could return. I said yes, they went on their way. A few weeks later they returned with another missionary. The first two were my age, just out of high school, the new guy was probably in his mid-late 20's.
So I got a lot of the same script, with a few extra details, but I still had questions. My questions started to visibly upset the older missionary, as he was getting increasingly more frustrated. In the end I didn't really get a lot of answers to the things I asked, and they left, saying they'd return later--which they never did. Now I'm not sharing this story to say "I got 'em" because that wasn't what I was trying to do in the first place, it was genuine curiosity, and I didn't think the questions I was asking were unfair or strange. As an example, when they explained that since Jesus organized His Church with Himself at the top with Twelve Apostles, that is how it was always supposed to be, which is why the LDS has a "Prophet"/President and a "Quorum of Twelve Apostles". My question, as I saw it, seemed simple enough: Who was in charge after Jesus ascended? I got a vague answer of "possibly Peter?" which made me ask, "Oh, sort of like the Pope then?" They didn't like that, and I followed it up asking "But wasn't Peter a member of the Twelve?" Which they also didn't like. Which is around the time the older missionary said it was time to leave and the other two younger missionaries followed without really saying much.
In addition to all this, there was also a very bizarre sensation I had throughout the whole exchange and encounter which I can't quite put my finger on. Which made it seem very unnerving. Something I can only describe as a general sense of emptiness, or darkness, like I wasn't talking to people who were thinking for themselves.
All else aside, I think there is a certain cruelty in sending what are often barely adult young people who are simply too young and too ill-equipped out and about. I can't figure out why, from a purely practical vantage point, that would make sense. Surely common sense would suggest that people you are trying to convert to your religion would ask a lot of questions and challenge certain assertions.
-CryptoLutheran