Kullervo was kind enough to point out that Protestant theologians have been tackling the Christian Unity problem lately in the form of a written debate and discussion of Peter Leithart’s call for a visible sign of unity between traditional Christians (during the oral discussion he explicitly said that Mormons wouldn’t be at the table.) The links Kullervo shared give a good rundown of the discussion held at Biola University and the aftermath.
If anything, it was good to know that somebody very smart can point to what seems a huge problem in Christianity with few, if any, practical suggestions on how it can be accomplished.
Leithart said something during the discussion at Biola that resonated with my observations of Protestantism:
All members of Christ, recipients of the spirit, baptism and confession of certain truths, is a visible expression of unity, but those expressions of unity have become meaningless in the face of our differences.
I think this is on point. Mormons are outside the boundaries because they don’t accept the summative doctrines of the creeds, but the differences between other Christian groups add up to dramatically different religious experiences, doctrines and spiritual foci. For a Mormon, the protestant world looks like a bunch of camps, with a barely visible unity, that essentially boils down to the Trinity, and often that doctrine is presented in a misleading or straightforwardly incorrect way. The lack of unity, or even a path toward unity makes the Christian world look less-than-Christian to those who are (by definition) outside the tent.
Also, even if Mormons are properly excluded from the big tribe Leithart advocates, the way Protestants deal with Mormons shows some of the same sort of tribalism he feels is a leprosy on the body of Christ. Identifying the tribalism on the margins of orthodoxy may help identify tribalism within.
From my perspective the entire discussion was very enlightening, and gives a very broad view of the differences between traditional Christians and why those differences matter theologically and historically. I would recommend it to non-traditional Christians as a snapshot of what matters between the varied versions of Christianity, and how the differences grew and how they are sustained.