Do Latter-day Saints consider Jehovah's Witnesses, Biblical Unitarians and any other groups that deny the divinity of Jesus to be 'true Christians'?

Question

Is belief in the divinity of Jesus an essential feature of a true Christian, according to Latter-day Saints? If so, would that imply that Christian denominations or groups that deny the divinity of Jesus, such as Jehovah's Witnesses and Biblical Unitarians, by definition, cannot be truly Christian?

Note: By true Christian I mean whatever Latter-day Saints mean by someone who is walking the narrow path that leads to salvation, according to the perfect will of God, following the example set by Jesus Christ for all believers to come.

Answer 1

Many years ago I created a simple statement...

I wish everyone would be Mormons...
Knowing that I won't see that, I wish everyone would be Christians...
Knowing that I won't see that, I wish everyone would be good people...
Sadly, I won't see that, either.

There are many people who challenge the right of members of the Church of Jesus Christ of Latter-day Saints to participate on this Stack because they don't believe we are Christians. This is entirely true — from their perspective, we do not believe in the same Jesus Christ, we do not accept their beliefs or their salvation, we are not part of their theology. Therefore, from their perspective, we are not Christians.

Ecclesiastically, the feeling is mutual.

And he said unto me: Behold there are save two churches only; the one is the church of the Lamb of God, and the other is the church of the devil; wherefore, whoso belongeth not to the church of the Lamb of God belongeth to that great church, which is the mother of abominations; and she is the whore of all the earth. (1 Nephi 14:10)

So when you ask the question, do we believe that members of churches that deny the divinity of Jesus Christ are Christians, as you can see, the question is somewhat moot. We believe there are two churches: the Church of the Lamb of God, the vessel of Christ's authority on Earth, the administrator of His ordinances... and everyone else.

Christians vs. christians

We do not deny at all that there is good in many (indeed, most) churches. We do not deny at all that there are good people who are not members of the LDS Church. Indeed, we do not deny at all that there will be people who walk the Earth who will receive exaltation in the Celestial Kingdom who did not join the Church of the Lamb of God in this life. (And, if you corner us, we'll admit that there will be too many members of the LDS Church who will find themselves in the Telestial and Terrestrial kingdoms, but that's a story for another day. No church can force a person to heaven.)

But we do recognize and appreciate that there are people in the Earth who are living christian lives, even though they either have not been offered the opportunity to embrace the Church of the Lamb of God, or do not understand the import of the offer, or have chosen not to do so. We believe this is worrisome because we strive to love all people and seek their best eternal welfare. But we recognize that many will not see that what is offered is a pearl of great price.

Not every one that saith unto me, Lord, Lord, shall enter into the kingdom of heaven; but he that doeth the will of my Father which is in heaven. Many will say to me in that day, Lord, Lord, have we not prophesied in thy name? and in thy name have cast out devils? and in thy name done many wonderful works? And then will I profess unto them, I never knew you: depart from me, ye that work iniquity. (Matt 7:22-24)

We also recognize that every other Christ-centered church on Earth will use that same verse against us. It was this very problem, the inability through the Bible to clearly identify which church was the true church of Jesus Christ that led Joseph Smith to pray and, through the blessing and marvel of God, change the world.

Conclusion

So, as you can see, your question is somewhat moot. Subdividing the various faiths into categories with the question, "do you consider them Christians?" doesn't make sense to us. Many will take upon themselves the name of Jesus Christ, and in so doing, are christians.

But few will embrace the fullness of the Gospel of Jesus Christ, few will apply themselves to His ordinances, performed with true authority (obviously from our perspective). Therefore, few will be Christians, meaning few have or will join the Church of the Lamb of God, the one true church compared to which all others, regardless their beliefs, are not.

Answer 2

As for the straight and narrow path, the gate is baptism (into the church):

2 Nephi 31:17-19

17 Wherefore, do the things which I have told you I have seen that your Lord and your Redeemer should do; for, for this cause have they been shown unto me, that ye might know the gate by which ye should enter. For the gate by which ye should enter is repentance and baptism by water; and then cometh a remission of your sins by fire and by the Holy Ghost.

18 And then are ye in this strait and narrow path which leads to eternal life; yea, ye have entered in by the gate; ye have done according to the commandments of the Father and the Son; and ye have received the Holy Ghost, which witnesses of the Father and the Son, unto the fulfilling of the promise which he hath made, that if ye entered in by the way ye should receive.

19 And now, my beloved brethren, after ye have gotten into this strait and narrow apath, I would ask if all is done? Behold, I say unto you, Nay; for ye have not come thus far save it were by the word of Christ with unshaken faith in him, relying wholly upon the merits of him who is mighty to save.

LDS don't go around telling people they are not Christians. LDS do go around telling people (also Christians) they still need baptism.

LDS don't point to doctrines and say "this is wrong" (ok, exceptions prove the rule). LDS do point to doctrines and say "this is right".

D&C 18:20-22

20 Contend against no church, save it be the church of the devil.

21 Take upon you the name of Christ, and speak the truth in soberness.

22 And as many as repent and are baptized in my name, which is Jesus Christ, and endure to the end, the same shall be saved.

(And since the other answer mentioned Church of the Lamb vs. Church of the devil, I would take this scripture to imply "the church of the devil" isn't simply "all other churches". The church of the devil is, in my opinion, probably invisible, not any specific visible organization / set of organizations. It's what is bad in every religion, tradition, philosophy, culture, etc. This is what needs to be fought. It's what opposes the church of the Lamb. What is good in every religion, tradition, philosophy, culture, etc. is what should be protected, affirmed and nurtured.)

Article of Faith 13

13 We believe in being honest, true, chaste, benevolent, virtuous, and in doing good to all men; indeed, we may say that we follow the admonition of Paul—We believe all things, we hope all things, we have endured many things, and hope to be able to endure all things. If there is anything virtuous, lovely, or of good report or praiseworthy, we seek after these things.

Answer 3

From a neighborly and cultural perspective we would certainly grant any person that is attempting to follow the teachings of Jesus Christ as Christian. As a member my whole life who grew up in Utah, I have never once heard of any certain denomination being singled out as non-Christian (though we definitely have our grumblings about certain denominations). In an informal setting we would not take it upon ourselves to argue someone's right to hold the title of "Christian" if that's what they want to be referred as. The main reason is that we don't care what people call themselves. We consider all other religions to be more-or-less organized collections of truths, errors, and traditions.

In a more formal setting with technicalities on the table, we would point out that we don't believe any other church at all has Christ's commission or authority to preach his gospel, and administer his ordinances. So in that sense, you might claim we don't believe any other church besides us is "Truly Christian".

Labeling ourselves or others as "Christian" just isn't much of a talking point for us because it's not very useful.

Perhaps a good standard for the term Christian, is someone who at least believes Christ will return

Alma 46: 15 - And those who did belong to the church were faithful; yea, all those who were true believers in Christ took upon them, gladly, the name of Christ, or Christians as they were called, because of their belief in Christ who should come.