I've noticed a pattern.
This is not any official church doctrine or even any unofficial church folklore. It's just an annoying habit that seems to be a frequent result from the Mormon mindset.
It seems that Mormonism teaches people to push doubts aside and ignore them entirely. I'm not talking about cognitive dissonance or confirmation bias (which are also big problems), I'm talking about something that seems more akin to selective hearing.
I've noticed this lately in internet discussions and realized that I've come across it before. On YouTube, TBMs commenting on exmo videos tend to get annoyed and exclaim vaguely that the truth has been twisted and distorted. When asked to provide specific examples, the vague exclamation is repeated without ever addressing an issue in detail.
It reminds me of the conversations I had with my father when I told him that I was leaving the church. I told him that I'd prayed about the Book of Mormon many times and never received the confirmation that I sought.
And he'd stare at me with that pained look in his eye, and say, "But why do you want to leave the church?"
"Because I don't think I ever really believed it," I told him. "After giving up on Moroni's promise, I looked back at some of the church doctrines and I realized I had a problem with some of them. I've never found a good reason for why the church banned blacks from holding the priesthood, and even the stuff with polygamy way back when seems pretty fishy."
And he'd look at me sadly and say, "But you haven't told me why."
Yes I did. How did he not hear what I just said? I just gave him three reasons why I left, and he still seemed to think that I hadn't provided any kind of explanation.
My mother had a similar reaction when she asked me why I wasn't going on a mission. I told her I didn't want to. She didn't try to address any specific concerns of mine...she just asked me how I couldn't want to.
Acknowledging the possibility of disbelief is put aside in favor of incredulity. How can you not believe? They're too bent out of shape over the impossibility of apostasy to worry about the reasoning. They don't want to hear the reasoning. They just want to hear the opposite of what they just heard.
I guess this is the mentality that leads to the simplistic dismissal of the apostate's reasoning, once it's been accepted that the apostate is actually doing the impossible. When they realize that someone can seriously decide to not believe in the church anymore, they begin writing that person's decision off as trivial--you left because you couldn't live the standards, you left because someone offended you, or you left because you wanted the freedom to sin.
From the beginning to the end of the process of apostasy, all an upstanding member of the church can do is assume that it's impossible to want to leave and if it is possible, it can't be because of doctrinal flaws.
And that doesn't seem right to me.