The reason for this is while the Mormons were starting their religion, they were persecuted. While some anti-Mormon literature was written, there was also a great deal of objective and firsthand accounts as well. If three different sources agreed on an event, it was unlikely to be pure hate literature. What I found out was very different from what I was taught growing up. The Church version of Mormon history is a heavily doctored one designed more for the raising up of faith than recording accurate history.
Independent research is highly discouraged.
Members are told to view, read, and listen only to Church approved sources. The more I learned on my own, the more I believed that Mormonism is not the true religion of God. The discrepancies between the historical and Church versions were so wide that I started to get angry. All my life, I was taught to believe that Mormonism developed in a certain way, and now it was all wrong. It got to the point that I wanted to sever every tie with the Church that I could.