Most of the time when the clergy make the charge that Mormons are not Christians, they are not thinking of Webster's definitions at all. The clergy defines the term for themselves, thereby thinking they control it. In this manner, the Latter-day Saints Could define the term CHRISTIAN to require a belief in the divine mission of Joseph Smith. This is foolishness. For Mormons to define CHRISTIANS as "people who believe what Mormons believe" and then reason that non-Mormons fail the Christian test would be nothing more than to say that non-Mormons aren't Mormons. Note that this would be without any consideration for what they may or may not believe about Jesus Christ.
So, those who reject the LDS do it in a narrow sectarian sense which actually rejects all those who doctrines differ from their own.
Those who reject the LDS on the surface make the strong charge that Latter Day Saints do not believe in Jesus Christ or do not attempt to follow His teachings.
So, the game is rigged. If you define a Christian as one who believes in the fundamentals of conservative Protestantism, as an example, then only they are real Christians. Playing this kind of word game is like defining a duck as an aquatic bird with webbed feet and a flat bill only to reject the male duck for having different plummage.

Mormons are Christians when they believe Jesus Christ to be God and live by His teachings as identified in the Bible.