Wikipedia
Anti-Mormonism is discrimination, persecution, hostility or prejudice directed at members of the Latter Day Saint movement, particularly The Church of Jesus Christ of Latter-day Saints (LDS Church). The term is often used to describe persons or literature that are critical of their adherents, institutions, or beliefs, or physical attacks against specific Mormons or the LDS Church as a whole.
Opposition to Mormonism began before the first Latter Day Saint church was established in 1830 and continues to the present day. The most vocal and strident opposition occurred during the 19th century, particularly during the Utah War of the 1850s, and in the second half of the century when the practice of polygamy in Utah Territory was widely considered by the U.S. Republican Party as one of the "twin relics of barbarism" along with slavery.
Modern-day opposition generally takes the form of websites offering alternative views about Mormonism or non-violent protest at large Latter-day Saint gatherings such as the church's biannual General Conference, outside of Latter-day Saint pageants, or at events surrounding the construction of new LDS temples. Opponents generally believe that the church's claims to divine origin are false, that it is non-Christian, or that it is a religion based on fraud or deceit on the part of its past and present leaders.