I can assure you that that depends on your definition of Christian!
Best,
inkling
I can find no example of any Christian denomination that has considered the question that accepts Mormons as Christians. Check the web sites for the RCC (the Vatican has it's own site, it's the best for this), the Lutherans, the Methodists, the Presbyterians, and the Southern Baptists. Go search on the terms "Mormon baptism". What you'll find is that these denominations have researched the issue and determined that there are some key LDS doctrines that are at variance with the canons passed by the early 3rd and 4th Century Christian councils and accepted as required elements of faith for anyone calling themselves Christian.
These include accepting the Trinity as one being, not three, and accepting Jesus as the only Son of God.
The LDS also holds the belief that there is another deity, God the Mother, and that God the Father and God the Mother procreate, producing spiritual children that are incarnated as humans on earth. Thus, Jesus is not the only Son of God, he's just the first born. And, finally for the purposes of this message, although there are certainly many other LDS doctrines at variance with Christianity, it is held that through faith and good works and obedience to LDS doctrines, humans can achieve divinity and, as married couples, graduate to become the gods of other planets, which they will then populate with their children as God the Father and God the Mother have populated Earth.
As I say, check the above web sites. Understand that this is not something I'm picking up as anti-Mormon rumor. I got this all from the above sources, which one would think would be reputable.
The whole thing came up as the question began to be considered, "Do Mormons need to be baptized upon conversion to < a_Christian_church >?" The RCCs decided "Yes", and then other denominations took up the matter and agreed. This is as opposed to the practice where, for example, a baptized Lutheran wouldn't need to be baptized again to become Catholic (although some other confirmation rite might be required). Once baptized as a Christian, always baptized as a Christian, regardless of the denomination you were baptized in. But if you're not baptized as a Christian, then you need to be to join a Christian sect.
So, while the word "Christian" is not copyrighted, and anyone can use it, I can't find any non-Mormons who consider Mormons Christian, while Christian denominations accord other Christian denominations that basic consideration, even though they may think that the other denomination is in grevious error and is in danger of damnation because of their practices.
Not.
Don't bother trying to explain it to them, you're wasting your time. Just follow the Savior's example and show your real faith through your good works.