D&C 121:39 says:
We have learned by sad experience that it is the nature and disposition of almost all men, as soon as they get a little authority, as they suppose, they will immediately begin to exercise unrighteous dominion.
Let me highlight a few phrases and explore their implications for us today.
We have learned by sad experience
This was written toward the end of the D&C, after multiple examples of people who had exercised unrighteous dominion within the Church - and even been chastised in the records that formed the D&C. This wasn’t theoretical or focused on “outsiders” and “Gentiles”. It included “saints” and leaders. It even included Joseph Smith, especially when it is viewed as the culmination of the section that starts with Joseph begging God to wipe out all those who had been persecuting the Saints. That aspect is ignored almost completely in most discussions about unrighteous dominion, but I believe it is critical in order to understand what this verse really says. Hence . . .
it is the nature and disposition of almost all men . . . immediately begin
The Lord couldn’t be clearer in using the words “almost ALL” and “immediately begin”. The temptation and tendency to exercise unrighteous dominion is nearly omnipresent within humanity and manifests itself immediately when authority is given or assumed.
get a little authority, as they suppose
There is a natural supposition about what “getting authority” means that lies at the heart of this issue - a misunderstanding of what it means to have godly authority and to what that authority is directed. The whole passage makes it clear that the authority is not directed toward control, but control is the central focus of authority for “the natural (wo)man”. Authority is supposed to mean something different in the Church (within the Gospel’s good news) than it does in the natural world. Almost all men, however, don’t make that distinction; therefore, they abuse Priesthood authority and lose the power that can be gained by becoming “unnatural” in this regard.
That fundamental misunderstanding is the heart of this issue - misunderstanding the principle that Priesthood authority only applies to performing ordinances and preaching the Gospel (according to Article of Faith #5) - not controlling others. (and, I would add, that this tendency exists in "almost all" women, as well - that "men" is used in D&C 121 due to the focus on formal offices within the Priesthood, but that the principle applies to almost all men and women - that this tendency can be seen in many, many ways and not just within the Church)
I believe the problem is that in order to avoid this natural tendency, the principle (the antidote) needs to be taught in the formative years before boys and girls become men and women - when they can learn to make the distinction and internalize the ideal. Much of the failing we see in this regard in the Church is because the sins of the fathers and mothers are visited upon the heads of the children - in this case, by passing on the tendency toward unrighteous dominion to their children.
The only antidote of which I am aware to the natural tendency toward unrighteous dominion is a relentless teaching of the principle of Priesthood as servant leadership within the Church, equally-partnered co-presiding in the home and “authority” as relating only to what is stated in the 5th Article of Faith. All of that is grounded in charity, so I also would suggest a steady dose of the Sermon on the Mount (especially the Beatitudes), 1 Corinthians 13 and D&C 121. If a young man or woman “gets it” when s/he studies those passages, especially, s/he can blunt the natural tendency to gravitate toward unrighteous dominion. It’s not quick, and it’s not easy, but it can and does work - and it’s critical.