To confuse matters further, William McGurn denounces the “cult” of Anti-Mormonism.
The answer is, it all depends on definition and context. Some years ago Walter Martin offered the following two indicators of a cult (from Kingdom of the Cults):
A cult might also be defined as a group gathered about a specific person or a person’s misinterpretation of the Bible (p. 17 emphasis in original). . . .
From a theological standpoint, the cults contain major deviations from mainstream Christianity (p. 18).
Those indicators are very helpful, especially the one about “deviations from mainstream Christianity.” However, that doesn’t completely solve the problem. First, we have to define “mainstream Christianity,” presumably using some of the great creeds of the faith, such as the Apostles Creed and the Nicene Creed. Assuming we can get agreement on mainstream Christianity, we face the larger problem that the word “cult” has a particularly ugly connotation in public discourse, reminding people of Jim Jones and the murder-suicide of hundreds of his followers in Guyana.
By that standard you could hardly apply the word to our Mormon friends. If you think about people along the spectrum of things like diligence, kindness, family values, integrity, generosity, and a host of other good traits, Mormons would rank as high (if not higher) than Baptists or Catholics.
There is yet a further problem. Christians don’t agree among themselves about who is and who isn’t “in the family.” I routinely hear people talking about “real” Christians, meaning that somewhere out there you can find a whole bunch of “unreal” or “fake” or “self-deceived” Christians.
I suppose we could say it this way. You can call yourself a Christian, but I don’t have to accept that as true. I do have to love you and be kind to you, but I am under no obligation to agree that you are a Christian.
That’s a hard concept for many secular or non-religious people to understand. The default position seems to be, “You’re a Christian if you say you are.”
Not everyone who says “Lord, Lord,” will enter the kingdom of heaven (Matthew 7:21-23).
In terms of basic difference, the following seems crucial to me:
Mormons do not accept non-Mormon baptism.
Christians do not accept Mormon baptism.
Furthermore, we do not believe Joseph Smith was a prophet of God nor do we recognize any Scripture apart from the Old and New Testaments. We heartily dissent from the unique teachings of the LDS Church and they heartily dissent from us.
That said, I doubt the wisdom of any pastor going to a basically political event and calling Mormonism a “cult.” While Jeffress later said he was speaking of a “theological cult,” meaning he was using the term in the Walter Martin sense, most people don’t understand that distinction.
To use the word “cult” in that setting (as opposed to a Sunday morning sermon where you can explain what you mean) invites unnecessary criticism.
As far as I’m concerned there is a great theological gulf between evangelical Christianity and the Mormon religion. So, no, I would not consider the LDS Church to be a truly Christian church because (to use Walter Martin’s term) they are outside of mainstream Christianity. That’s a theological statement, not a judgment on any particular person.
Meanwhile, we can be good neighbors and even close friends while we agree to disagree and sometimes warmly debate the differences between us.