How does any group of people achieve harmony/unity in diversity?
It's easy to say everyone should agree, but what does that really mean? No two people agree perfectly on everything. People don't even agree with themselves; we all change our minds, our preferences, our priorities, etc.
With the tremendous variation of backgrounds, education, culture, and worldviews among people generally, and Latter-day Saints specifically, what does it mean to have harmony and unity instead of disputations and contention?
Clarity. Whenever there is a disagreement, the first objective must be clarity. Often disagreements arise from misunderstanding, and clarity can resolve misunderstandings. Clarity will reveal whether there really is a disagreement, and whether it is material. If so, is the disagreement about objectives, values, and ideals, or is it about the means to achieve a common objective? Is there a disagreement about underlying facts, assumptions, inferences, etc.?
Charity. After clarifying the issue(s), those involved with the disagreement can invoke harmony by giving one another the benefit of the doubt, including the mutual assumption that everyone is acting in good faith. This means implementing the six principles President Nelson offered while observing that "Charity is the antidote to contention" [see below]:
Express feelings with love.
Don’t think you know best.
Don’t rigorously defend your position.
Let the Spirit guide your conversations.
Be filled with charity, the pure love of Christ.
Understanding. The fundamental reason for contention is the impulse to seek conformity to one's own position, beliefs, priorities, etc. People contend because they want someone else to change, without realizing (or accepting the possibility) that maybe they are the ones who should change.
When parties to a disagreement seek to "understand" instead of to "convince," they eliminate the utility of contention. They may come to a meeting of the minds and replace disagreement with agreement. Or they might not.
And it doesn't matter.
People who fully understand one another can live in harmony and unity despite their differences. They can "agree to disagree" and actually mean it.
One of the classic "7 Habits" is "Seek first to understand, then to be understood."
This habit involves listening effectively. But to completely eliminate contention, understanding is not enough. They must be comfortable with different ideas.
Multiple working hypotheses. Even after people achieve clarity, charity, and understanding, they may realize they still disagree for any number of reasons. Often the differences involve gaps in knowledge. While people await more information, they fill in the gaps according to their own assumptions, inferences, etc.
In this situation, people can accept the concept of "multiple working hypotheses," whereby different people are all at peace knowing that other people see things differently. This involves a paradoxical combination of confidence and humility; confidence in one's own views together with a humble recognition that someone else might be correct.
Some people may prefer a variation of multiple working hypotheses which treats much of reality as subjective and thus not subject to unanimity.
Paul offered a solution when he was told there were quarrels/contentions among the Corinthian saints:
1 Corinthians 1:10
King James Version
Now I beseech you, brethren, by the name of our Lord Jesus Christ, that ye all speak the same thing, and that there be no divisions among you; but that ye be perfectly joined together in the same mind and in the same judgment.
New International VersionI appeal to you, brothers and sisters, in the name of our Lord Jesus Christ, that all of you agree with one another in what you say and that there be no divisions among you, but that you be perfectly united in mind and thought.New Living TranslationI appeal to you, dear brothers and sisters, by the authority of our Lord Jesus Christ, to live in harmony with each other. Let there be no divisions in the church. Rather, be of one mind, united in thought and purpose.
So, in moments when we disagree with others, we have the choice to either allow our differences to end in contention—pushing us apart and potentially damaging our relationship—or allow the disagreement to help us have a new understanding and appreciation for those we disagree with.