"Many Christians" are not correct. Reorganize Church of the Latterday Saints have ALWAYS been Christian and have since changed their name. Latterday Saints have also been Christians from day one.
Claiming Christianity is not the same as actually being Christian. Taking the Bible, 40 books written by multiple authors across generations, that all denominations of Christianity base the religion on and making it secondary to a book written by a single person in the 1800's is NOT Christianity. It's co-opting an established religion for your own doctrinal gain.