Dr. Guy wrote a piece on the leader of the Fundamental Church of Jesus Christ of Latter Day Saints, or, the FLDS, a Mormon splinter group that most in both the Mormon community and the larger Christian community at large consider to be a cult. In response, a blogger who is a member of the Salt Lake City based Church of Jesus Christ of Latter Day Saints (the group known to most of us as "the Mormons") stated that Warren Jeffs was not a Mormon. I take issue with this statement, although it is common among Mormons.
See, for many years, many in the evangelical community have denied that Mormons are Christians. They've attached some rather nasty labels to it, although most Mormons consider themselves Christians, and they are considered by the majority of leaders among world religions to be a Christian sect. The logic is that Mormons have a right to self define themselves as Christians, because they recognize Jesus Christ, even though their understanding of His person and work might differ from the understanding of other sects.
The problem is, many of these Mormons are not willing to extend the same courteousy to sects within their own faith, such as the FLDS, or other splinter groups (most of whom, for the record, do not currently practice polygamy). If they do not recognize the leade or the SLC church, you are "not Mormon".
But, the FLDS church defines itself as Mormon, and, in some ways, its practices are closer to those of the founders of the original Mormon church. While some of their beliefs may differ strongly (although many early leaders such as Joseph Smith and Brigham Young did practice polygamy, they did not practice the strict control practiced by splinter groups led by people like Jeffs, and their actual practice of polygamy was quite different from the way the FLDS church practices), the FLDS nonetheless has the same right to self define its identity as do the SLC Mormons. While it's certainly fair to refer to the FLDS as a "splinter group", or mention that they are not affiliated with the SLC church, they are nonetheless Mormon in the strictest sense of the word, just as Mormons are Christians in the strictest sense of the word.