What I find most ominous about the way that so many mainstream Christians reject the Christian status of the CJCLDS / Mormon church - is that the grounds on which they do so would also reject the vast majority of past and present members of their own Catholic and Protestant denominations.
In practice, many mainstream Christian intellectuals regard philosophical doctrines as more important than Christianity; in the sense that they cannot believe that anyone who rejects their philosophical doctrines can really be a Christian.
This formally entails that their understanding of Christianity is contained-within the philosophical doctrines of Catholic or Protestant theology; or those bits of Catholic and Protestant theology which overlap.
To put it crudely, they put philosophy first, and fit Christianity inside it; and assert that anything outside the philosophy cannot be Christian
What does this mean for the mass majority of Catholic and Protestant children, simple people, and others who either cannot understand these philosophical doctrines, or cannot hold them in mind, or in actual fact believe in a God the Father and Jesus Christ who have (to all intents and purpose) exactly the same nature as is understood by Mormons?
This must, indeed, be the case - because ordinary simple people simply cannot comprehend what it means to create from nothing, or to have a disembodied God who is located everywhere, or to have a Holy Trinity which both is three and one simultaneously - what is actually in their heads is pretty much what Mormons have as their 'official' doctrine.
Now either these Catholics and Protestants who actually believe in the Mormon God and Jesus are not really Catholics or Protestants; or else we regard being Catholic or Protestant as being merely a submission to a structure of authority and passive assent to a set of un-comprehended verbal forms.
This is a terribly hazardous situation - not for the LDS, which is doing fine, and indeed is perhaps more devout than at any time in its history - but hazardous for Catholic and Protestant Intellectual Christians; because the temptation is to misrepresent Mormon beliefs - in order to be able to deny that Protestants and Catholics actually hold them - is hard to resist, and is clearly seldom resisted.
The misrepresentation of Mormonism ranges from an ignorance which is understandable, yet is proud, wilful and refuses correction; through to an ignorance which is based upon pervasive bias; to a deliberate focus upon decontextualized peripheral aspects of Mormonism (pulled-out and held-up for ridicule as obviously crazy) while ignoring the core of actual Mormon beliefs and practices as they are lived; to plain and straightforward lying about Mormons (dishonestly rationalized by the desired-for end - of destroying the LDS church - justifying the means); to what I can only regard as a near-psychotic craziness on the topic of Mormonism which refuses to see the plain and obvious present day known realities, and instead focuses on the open-ended realms of the hidden and unknown, the arcane, the potentially possible, supposed analogies with other religions, and whatever evils attributed to Mormons (someplace at some time) that cannot conclusively be disproved.
(And, as always in human affairs, there are those Christians who are simply looking for an excuse to indulge in the exhilarating emotion of unrestrained hatred; in which case, unless this pleasure-in-hatred is repented, they may not remain Christians for very long.)
Now - of course I do not expect that either Protestants or Catholics ever could or would accept Mormon theology - it is profoundly different, profoundly in the accurate sense of different way back at the level of metaphysical assumptions.
Also there are additions to Mormonism compared with Catholic and Protestant beliefs. But then there are additions (loads of them, and very profound ones!) in Catholicism as compared with Protestantism; and in many forms of Protestantism in actual practice - which incorporate magic, animism. Indeed, in general, since Protestantism lacks a central authority - and many forms have a very local form of organization, there are almost as many types of Protestantism as there are churches, home groups or individual worshippers. Who knows what additions, combinations, or new emphases these may have?
And I accept that there is evidence on both sides of Mormon claims. Certainly the evidence is not overwhelming. There is some good evidence that the LDS church is true (in the sense of essentially what it claims to be), and also some good evidence that it is not true: the evidence is in some kind of balance. In other words, the evidence either way is not decisive. The choice between the possibilities is a choice, the decision is not-compelled, and the choice must be made by each person.
Furthermore, the way that Mormonism was set-up, and the highly specific and concrete nature of its claims, leaves very little 'wriggle room'. This means that there are only two informed coherent attitudes to the CJCLDS - that it is true or it is a fraud: a deliberate deception by the founders and sustainers.
So, the crux is that for Mormon unbelievers the choice is between on the one hand regarding the religion as a benign fraud - and on the other hand, regarding Mormonism as a fraud that is covertly malicious (since there is so little/ zero evidence of overt wickedness).
Nonetheless, if we are both honest and informed, it must be acknowledged that precisely this situation exists between all Christian denominations - that either someone else's denomination is true or a fraud; and that any Christian faith which comes from another denomination must be attributed to ignorance or accident.
However - this should never lead us to deny the reality of Christian belief in despite of what inevitably seems like organizational fraud, or doctrinal ignorance.
We must have a concept of Christianity which fully and at the highest level encompasses the faith of the the simple and the ignorant - and those of other Christian denominations who live by Christ, as best they may (which may be very well indeed, and far better than the intellectuals who profess to judge them on philosophical grounds).
(I know that some will allow that individual Mormons may be Christian, but hold that the LDS church itself is not Christian. And they regard this as a problem because they believe that false theology will lead - sooner or later - to apostasy, and evil. Yet the apparent fact that this has not happened in the CJCLDS must either challenge their belief, or encourage them to look hard for signs of apostasy and evil in the modern Mormon church - evidence that it is going-bad; and if you look hard enough, you will of course find what you seek. Also, it is obvious that 'true' belief in a church does not prevent apostasy, or error or corruption. Thus the relationship between philosophy/ theological detail/highly specific official doctrine on the one hand - and on the other hand goodness and Christian faith is... well, at best extremely weak and probabilistic.)
So, the status of being 'a Christian' must - and I really mean must - be non-philosophical and extremely simple; or else we will do terrible damage both between denominations, and also within denominations.
Therefore, the specific example of Protestant and Catholic attitudes to Mormonism leads us to a very important general topic that transcends the specific question of the CJCLDS - i.e. the definition of being 'a Christian', as contrasted with the definition of any particular Christian denomination.
I contend that the apparent desire to enforce a definition of Christian which includes both Catholic (Eastern and Western) and Protestants, yet excludes Mormons, will lead to falsity and wickedness - will indeed stoke hatred within-denominations and between sincere self-identified Christians; and will, in short, play-into the hands of the Enemy.
Because, a definition of 'Christian' which includes Protestants and Catholics yet excludes Mormons, will also and inevitably exclude most of the simple, the ignorant, the isolated, and the children among Protestants and Catholics.
Thus I would expect that honest and informed Protestants and Catholics would accept that it is possible for Mormons to be Christians (and good Christians) despite the philosophical/ metaphysical differences.
And if they do NOT accept this, then they need to agree that if Mormons are not Christians due to (for example) their supposed misunderstanding of the nature of God the Father, Jesus Christ and the Holy Trinity - then the clear implication is that many and probably most Catholics and Protestants throughout history have not been Christians for exactly that same reason.