Two great obstacles in Mormon history are institutional lying and inner secrets. Both have been built into our faith. When Joseph Smith was confronted with plural marriage in a society that would be scandalized by such a practice, he hid it from public view. We all know the public statements and even scriptural declarations about marriage between a man and one wife were belied by the private practice of Joseph Smith. Therefore, our religion's history starts with a gap in telling the truth. We accept the fact that church leaders, beginning with Joseph Smith, lied to the public. There was an "inside" story and a "public" story. This is a problem for Mormon history.
Second, any Latter-day Saint who has been through the temple is aware there are things we regard as sacred that we just don't talk about. We keep secrets. Our faith reaches its deepest meaning in an atmosphere of secrecy and hidden knowledge.
When these two parts of the faith are present, it creates a challenge to telling our history in a frank, forthright and true manner. You must create filters in your analysis to account for the presence of these two skewing factors. One of the most significant historic disputes between the RLDS (Community of Christ) and the LDS church arises from this very problem. Emma taught Joseph Smith III (and her other children) that their father never practiced plural marriage. So when "young Joseph" came west, he was shocked by the stories and thought (at least initially) that the Utah Mormons were lying. Emma used well known public statements of Joseph denouncing "polygamy" as well as several canonized statements on the subject to support her claim that Joseph never took other wives. To reconcile it all a person must come to grips with the fact that Joseph Smith was not telling the truth to the public. There are echoes of this disparity still today.
Plural marriage caused the hierarchy to lie to the public. They did it when plural marriage was both coming and going. It was practiced in private, shielded from public view and shrouded in lies, both before it was acknowledged in 1853 and after it was publicly abandoned by the Manifesto in 1890. The Manifesto was a public relations document intended to hide the fact the church was continuing the practice. There are too many available sources now in public to claim otherwise. But the adoption of Official Declaration 1 makes it awkward to admit the practice continued. So most church members are unaware that it continued in secret even after the Manifesto.
Oddly, neither Joseph Smith nor the church itself could pass a temple recommend interview. ("Are you honest in your dealings with your fellow man?") Any faithful Latter-day Saint with just a small amount of knowledge about our history knows the church and its leaders have been less than honest in the past to prevent the public from knowing what they were doing.
In saying that I want to be clear. I am not condemning the church. There were sufficient reasons for these public dis-information campaigns, and there has been a theological justification used to defend the practice. The church has pointed out that Abraham said Sarah was his "sister" rather than to candidly acknowledge she was his wife. But the theological implications are not what this line of discussion is about. So I'm leaving that topic unaddressed.
The bottom line is that when you attempt to unravel the church's history, you must contend with the fact that the church has a history of dissembling. They publish lies to prevent embarrassment or prosecution. You must include a filter, or detector, or whatever you want to describe it as, in order to arrive at the underlying truth.
The idea something is "sacred" is also important in understanding our history. It has been used to compensate for missing revelation. At one extreme the leaders are thought to meet regularly (every Thursday) with Jesus Christ in the Temple. Under this happy view, the leaders are never wrong because they're just doing what Jesus says each Thursday. To suggest this may not be the case is so foreign a concept to these people that anyone who does so is weak in the faith and on the road to apostasy. Therefore, you must also account for the mythical elevation of leadership through the "too sacred to discuss" veil which makes honest analysis difficult and emotionally charged.
These are two great challenges to anyone trying to know the truth. Any person seeking to understand our history must account for both as they evaluate the events.