I may add to it from time to time. I'll improve responses from time to time as well.
Background. People promote M2C* because they think that, if the Book of Mormon is a real history, it can only have taken place in Mesoamerica. This makes them equate the truthfulness of the Book of Mormon with M2C. That raises the stakes for M2C to the highest level, especially because M2C is being taught by CES and BYU.
M2C teaches that the Hill Cumorah of Mormon 6:6 must also be in Mesoamerica. New York is too far away from Mesoamerica to satisfy the M2C interpretation of the text. This means that anyone who has taught that Cumorah is in New York must be wrong.
M2C advocates explain that all the prophets and apostles who have taught the New York Cumorah were merely expressing their opinions, as men, and were neither inspired nor spoke from personal experience.
Many members of the Church disagree because they believe the teachings of the prophets and apostles about the New York Cumorah.
Claims. Some of the quotations in blue below are taken from social media, others from various book and articles. I don't provide the sources because none of this is personal and because the authors could change their minds, but anyone can google the passages to see where they originate.
This argument raises the obvious point that there are no first-hand accounts from Moroni as a resurrected being, nor from Moroni, Mormon, Nephi, and other Book of Mormon authors. At best we have Joseph Smith's second-hand accounts of what they said and wrote.
The claim asserts that these are not first- or second-hand accounts. It's not clear what the claim means. Brigham Young reported Oliver's statement; i.e., he heard it from Oliver. That makes Brigham a first-hand witness of what Oliver said.
In a courtroom, this would be inadmissible hearsay if it was offered to prove the truth of what Oliver claimed about visiting the depository. However, if it was offered to prove the fact that Oliver said the words, then it would be an admissible a first-hand account. David Whitmer's statement is the same.
This is important because their first-hand testimony provides context for a first-person account by Oliver Cowdery; i.e., Letter VII, in which he declared it was a fact that the final battles of the Nephites and Jaredites took place in the mile-wide valley west of Cumorah. (see next claim).
If M2C is claiming there are no first- or second-hand accounts because everyone involved is dead, and we can only read the written version of their statements with no opportunity to cross-examine, then every historical document is at best second-hand. In this case, Brigham Young's speech was recorded and published in Journal of Discourses. If everything published in Journal of Discourses and other historical documents is merely an LDS "urban legend," there can be no fact claims based on historical evidence.
First, absence of evidence is not evidence of absence. Joseph and Oliver never detailed all the revelations they had, such as the things they prophesied when they were baptized. They didn't even detail the visit of Peter, James and John. They just declared it had happened.
Likewise, President Cowdery just declared it was a fact that the final battles took place in the mile-wide valley west of the Hill Cumorah in New York, and that the depository of Nephite records was in that same hill.
Second, "persuasive" is in the eye of the beholder. Because of bias confirmation, people readily accept false accounts if they confirm their biases, and readily reject objectively verifiable facts if they contradict their biases. Whether the prophets explain their statements of fact to the satisfaction of any particular reader is up to that reader. The vast majority of the people in the world don't believe even the published revelations.
Third, the requirement of a "revelation" compounds the error of claim #1 above.
Joseph did not claim a "revelation" about the dimensions of the plates; he learned that by physically holding them. He didn't claim a revelation that the Title Page was a literal translation of the last leaf of the Harmony plates; he learned that by translating the plates.
If, as he claimed, Oliver Cowdery actually entered the depository of Nephite records in the New York Cumorah, he would not need a revelation to tell him what he physically experienced.
Oliver was present when the divine messenger said he was taking the Harmony plates to Cumorah. He visited the hill Cumorah with Joseph Smith to observe Moroni's stone box. He told the Indians that it was Moroni who called the hill Cumorah anciently.
Recall, we are talking about the Assistant President of the Church, a position higher in authority than the First and Second Counselors in the First Presidency.
This claim is merely a pretext for rejecting the teachings of the prophets because the M2C advocate disagrees with what the prophets have taught.
M2C is the acronym for the "Mesoamerican/two-Cumorahs" theory of Book of Mormon geography. This is the idea that the Hill Cumorah of Mormon 6:6 is somewhere in southern Mexico, not in New York. The "hill in New York" where Joseph Smith found the plates was named Cumorah in the early days of the Church as part of a false tradition.