At first I thought "Hold on, I believe that too, but Mormon's can't be Christians, can they?"

And on the onset, it appears that we've got some common ground here.  I mean, I believe in Christ, his teachings, his example and I would also agree that genuine following of Christ will also emulate his pattern of living.

So what's the big deal?

Truthfully there is a big deal and the big deal is in the basic fundamental doctrine of the Mormon church in:

The problem with this video is that it assumes a false premise, the proposition being that it's an opinion of these people in the video that makes the answer true or not.   The truth being, only the Bible can answer this question.

If we break down faith in Jesus Christ, we will see that the Bible teaches a very different account of the divinity and the true nature of Jesus than the book of Mormon, Doctrine and Covenants, and the Pearl of Great Price.

The Bible teaches a divine / triune God with three equal and distinct people being the Holy Spirit / the Father / the Son. Also, that there is only One God and only will be One God in all the universe for all time.

Mormon doctrine teaches Jesus as the spirit brother of Lucifer a created being by Heavenly Father and Heavenly Mother, and his mission as saviour is a part of the process of "Eternal Progression".  That by following the ordinances in the temple that you will also become a god.

The Bible teaches that sin was wholly paid for by Christ, on the cross, by his blood, for all time.  And that it is a free gift to those who will accept it, there is nothing extra that can be done to achieve or accept salvation.

Mormon doctrine teaches that Christ's sacrifice, temple baptism, temple endowment ceremonies, receiving the priesthood, striving to a perfect life and "doing all you can do" will gain your entry into heaven and into God's good graces.

The big problem? we are talking about two different Christ's.    This is a big problem because of Matthew 7:21-23.

Mormon's believe that Joseph Smith was a prophet of God.  Joseph Smith report-ably wrote the Book of Mormon (however some other evidence states that perhaps it was actually Oliver Cowdery or Sidney Rigdon) as direct inspiration from the angel Moroni.

The full title to the book is more accurately "The Book of Mormon, Another Testament of Jesus Christ".  They try to pull Jesus into this book as well.  This book is horribly inaccurate when it comes to archaeology, copies large sections of the Bible and is changed from time to time when a leader of the church feels the social pressure to make the change (blacks and the priesthood, feminism and heavenly mother)

The Big Problem?  Joseph Smith made many prophesies in his lifetime (you can view  a bunch here http://mit.irr.org/false-prophecies) and was also likely convicted of fraud in 1826 (there's some debate about this).

Prophecies are what define a prophet,  if their predictions don't  come true then they are to be easily regarded as a false prophet.  No feelings involved, no credit for good behaviour,  they simply did not speak for God.  Which means they lied, so what else have they lied about?

Not to mention that he taught:

Most doctrines of the Church stem from what Joseph Smith and subsequent LDS leaders taught. Many of them range from outrageous to outright awful.

So, is a Mormon a Christian?  No, a Mormon is a Smithian, a follow of Joseph Smith, paying lip-service to Christ.