(EDIT: Made several revisions based on the feedback. Perfection isn't possible, but I've cleaned up where I can. Thank you, everyone.)
Two months ago, we witnessed something historic. And it kind of got lost in the shuffle of some other historic political events: We re-elected a black president for the first time ever, and we elected more female senators than ever. But something else happened: Gay marriage rights went 4-for-4 at the ballot box. After so many near misses, after so many hard-fought campaigns, all of a sudden, the forces of love started to win. And if the current trends continue--younger Americans tend to be far more tolerant of homosexuality than older Americans do--these victories will not be temporary. Look at the long-term trend: Being gay is becoming as normal as being, well, a human. Because people are slowly realizing that gays, bi's, and straights are all humans.
How did we get to this point? As a straight male with a rather limited knowledge of this subject, I can only toss up my perception from the outside looking in. But as someone who had to unlearn homophobia--yes, I used to be a Far-Right conservative--I can offer my two cents. I think that the growing success of the gay rights' movement in part comes down to three aspects.
(Discussion below the fold.)
1. Peaceful persistence. Even a casual study of just about any civil rights movement shows a common theme: When the oppressing and the oppressed sides clash, wrongdoings from the oppressing side are downplayed, but wrongdoings from the oppressed side are blown out of proportion. Gandhi knew this well and made it absolutely clear to his supporters that they could not, under any circumstances, retaliate. Responding to hate with hate has simply not been a part of gay rights. Now yes, there have been episodes such as the Stonewall Riots where circumstances got so bad that there was little choice but to fight fire with fire. But the last time I checked, LGBT advocates never resorted to terrorism, mass violence, or even mass bullying. Consider how badly it might have backfired if some LGBTs had responded tit-for-tat to bullying incidents: Much progress would have been lost, and the forces of hate could have used those incidents as smokescreens. The irony is that oppressed groups deserve to be angry; they deserve to be upset at those who place their egos ahead of other people's basic rights. It would almost be justifiable to retaliate. But that is not what they have done. They made straights realize that they are simply the target of a problem they did not create, not because of their sexual orientation, but simply because straights chose to create it. And many straights woke up and realized it.
2. A desire by many to join mainstream culture. Historically, Americans have had some real trouble getting along with people that are not "one of them." However, when newcomers show a genuine desire to assimilate into mainstream culture, most of the time the barriers eventually start to come down. Gays were no exception. Consider this: one of the great running jokes in the 2000s was the truth about the "gay agenda." It usually went something like this: Wake up at 7:30, breakfast at 8, drive to work at 8:30, meeting at 10, etc. The point was, many gays just want a normal life like the rest of us. When enough people started to realize this, they began to lay down their arms. They were scared over nothing!
(Edit: This is where I really had to fix things up. Some LGBTs want to mostly blend into mainstream society, and some do not. But I do maintain that the fact that quite a few of them wanted to integrate did help speed up the process. Americans, after all, are a notoriously xenophobic bunch; when an "other" group comes seeking equality of status, the former sometimes feel they have less to lose when they feel they have less to change. Whether this was a necessary process, however, is a question that I do not feel qualified to answer.)
Before I continue here, a word of caution. If one simply reads this list and leaves it at that, one might get the impression that it was gays who bore the responsibility to somehow prove their worthiness of acceptance into society. Nothing could be further from the truth. It has been, and always will be, a responsibility of straights to treat gay people as people. Blaming gays instead of straights for homophobia makes as much sense as blaming shooting victims instead of shooters. And that could be said for a number of other causes.
3. Inclusiveness. Had gay rights activists claimed that the only way to really know what it's like to be gay is to actually be gay, they would have walked right into the trap that gays are somehow fundamentally different from straights. While it technically would have been true to claim the former point, they instead explained to us how that gays and straights are almost identical, with the only real difference being whom their hearts compel them to love. They showed us, in language that we straights could understand, how little sense it makes to deny a couple's right to express their love, simply because other people found it icky or a religious book said it was bad. And do not underestimate the importance of gay-straight alliances. By recruiting anyone of any stripe who was willing to join the cause, they greatly increased their power.
The victories will continue to come. Gay marriage is now legal in nine states, and I'll bet we're a lot closer to legal in all 50 states than some people realize. All it will take is one resounding Supreme Court victory--which is not out of the question--and boom, we're there. Hang in there--It gets better.