More importantly, they're winning.
Since god always plays on the winning side we can see where god wants us to be.
You might have meant this facetiously, but in actual fact American Christians, like many people, do judge which side God was on in retrospect by the course of history. In liberal Christian churches, for instance, I've heard often about how the divine will gave courage to the Civil Rights protest marchers, gave eloquent expression to the thoughts of the Rev. Dr. King, and opened many peoples' eyes to the bigotry behind segregationist politics. Eventually this was sufficient to move even the "prophets" of the LDS to change their minds about what they thought God willed.
A century or so earlier, the same thing happened with regard to American slavery. Now, the same thing is happening, and will happen, with regard to gay rights and sexual tolerance.
Of course, those on the other side of such moral struggles never perceive them as a process of coming around to the true plans and desires of a caring God, but instead, as the insidiously growing influence of the devil. (Which then furthermore leads to the conclusion that for the devil to have acquired such power to thwart God's will, we must be living in the End Times.) The fact that they're choosing to exalt the devil's strength and belittle God's, such that every time they see moral change happening they immediate conclude "the devil's causing it," never seems to faze them. It is only in the rear view mirror that they can see which side the devil was really on.
(A few centuries earlier still, something very similar to this happened with regard to witchcraft, in a remarkably short interval. Within just a few years after the Salem witch trials, which were seen and written about at the time as not only a war but a "last stand in the new world" against the rising power of Satan and his recruited minions, it was not the numerous surviving accused witches but the accusers and judges who were publicly declaring their repentance for having been under Satan's influence. [In many ways, the aftermath of the Salem trials is a more fascinating subject for historical study than the trials themselves. The community didn't just shrug and say "glad that's over" and move on. There were intellectual and emotional tidal waves that are still relevant today.])
Whether it's due to the influence of the Holy Spirit overcoming the devil, or just the moral consensus of mortals evolving over time, the LDS and their "prophets" will soon have their eyes opened, as they have before, to which side they should have been on. Proposition 8 was a moral test for them, a temptation if you will, and they will come to realize that they failed it like the God-fearing citizens of Salem failed theirs.
Or if not, then despite their resilience in the past they will this time end up marginalized, like such formerly upright and respected organizations as the House Un-American Activities Committee and the Ku Klux Klan.
Respectfully,
Myriad
