According to the
: "Some early Latter-day Saints were Masons. Heber C. Kimball, Hyrum Smith, and others belonged to Masonic lodges in the 1820s, and Joseph Smith joined the fraternity in March 1842 in Nauvoo, Illinois.
Soon after he became a Mason, Joseph introduced the temple endowment. There are some similarities between Masonic ceremonies and the endowment, but there are also stark differences in their content and intent." Mormons are perfectly fine with Freemasonry. My Schooling was in World religions and Mormonism was one I have written for extensively due to the amount of open research is available to use for parallel associations.
The first thing is Mormonism is Non-Trinitarian, which means the Father is not the Son and not the Holy Spirit and not the Father, etc. So God is not triune in equality. They believe Jesus is a Son of God, who did die for our sinful natures. They also believe he came to the lost tribes of Israel whom were located in ancient America, which is what the Book of Mormon is written in regards to. The LDS is headed by a living Prophet who can change religious text at any time, which means you can take an old Book of Mormon or Pearl of Great Price and compare it to a modern printing and find major changes, even to the outcomes of the stories within. They believe married women cannot enter Heaven without the permission of their husband. At one time, I do not know when it changed but apparently it did, people of color were not allowed to become members of the LDS because according to their Book, People of Color were cursed by God.
Overall, Mormonism is just another branch of Christianity most Christians despise because they added additional books, kind of like how Christians added books to the Jewish texts- go figure. Fair play.