With some modification and the addition of some sources from reddit user jamesallred’s post here

A common argument amongst mormon apologists and some leaders today is that The reason you (the unfaithful) no longer believe the church is true, is because YOU started with the wrong assumptions.

Here is an example from the Givens’ book A Crucible of Doubt.

(speaking of “erroneous assumptions”) “They point us in the wrong direction, limit our understanding, and even warp the questions we ask. Worse, they create the conditions for faulty reasoning and disastrous conclusions.

Here is an example from FairMormon:

Faulty assumptions about what we should expect from prophets, scriptures, or even from God, can set us up for problems when these assumptions are not met.

But where did these “faulty” assumptions come from?

Arguably, the Church supplied these faulty assumptions, assumptions that I now have good reason to believe are not true or at least deeply problematic.

These are the kinds of assumptions I had about the truth claims of the Church as a believer that were fed to me by Prophets, seminary teachers, Bishops and during thousands of lessons.

Faulty Assumptions:

  1. A prophet will never lead us astray. (Wilford Woodruff; emphasis and elaboration on lds.org)
  2. Brigham Young never taught the Adam/God doctrine. (see public statements by McConkie and Boyd Kirkland’s letter)
  3. The Book of Mormon contains the fulness of the gospel and is a real history of real people in a real place living at in a specific time. (for example, Your Fringe Benefits)
  4. The temple ceremony is a restoration of true ceremonies practiced by Adam and in solomon’s temple. (for example, “We have the true Masonry. The Masonry of today is received from the apostasy which took place in the days of Solomon …” from here)
  5. Polygamy was about helping widows and because there were more women than men. (seems to have been a “common justification”, see here, or here)
  6. The spirit is easily offended and won’t be with you if you even sin a little. Prophets live a higher law than normal mormons to be worthy of this spirit and be in God’s presence. They would never lie. They would never break the law. They would never destroy people just because they were getting in the way. They are nice kind and righteous grandfatherly figures. [sources?]
  7. Joseph Smith literally translated the Book of Mormon. (literal translation: 1, 2, 3, 4, etc; Royal Skousen: “Is [it] a “literal translation” … no)
  8. Joseph Smith literally translated the Book of Abraham from Papyri literally written by Abraham. [sources?]
  9. Priesthood power is real and can heal people and perform miracles. [sources?]
  10. Tithing opens the windows of heaven and provides financial blessings if you obey. [sources?]

The church provided these assumptions—I did not come up with them on my own.