Timothy Kincaid exposes DADT defenders like Congressman Mike Pence:

[A]chieving the best Military is of no consequence to those who are leading the public opposition to open service. If irrefutable proof were offered that open service by gay personnel would increase unit cohesion and military effectiveness by 25%, they would still be opposed. Because their chief objection has nothing to do with the military, the fears of other soldiers, or even sensitivity to the religious teachings of chaplains. No. Their objection is based on the fear that open service would remove the stigma and hostility that is institutionalized by the DADT policy. They don’t care about military policy nearly as much as they do about condemning homosexuality and gay people.

I think many under-estimate the symbolic importance of this to those who believe homosexuality is a sickness or a sin. What we are asking of them is not simply to tolerate reluctantly the fact that some gay people refuse to be ashamed or closeted, but to conflate the symbol of the American soldier with a homosexual. There are very few emblems in American life that carry the weight, power and symbolism of the American soldier, the veteran, the men and women in uniform.

To say that open gay men and women are serving their country in uniform is to say that they are fully citizens. It is this equal citizenship that simply cannot compute with the idea of homosexuality in the minds of a minority of the older generation.

It moves the debate from "we tolerate you" to "we are you" and "you are us." The same with marriage equality. This is what the holdouts cannot tolerate. Because they realize they will not just have to tolerate but to honor a gay person. And they will have to honor him or her because that is their own value system, being required to integrate citizens who were once defined as the "other" in every imaginable way.