Ta-Nehisi Coates thinks so:
Bigotry is the heaping of one man's insecurity on to another. Sexism, racism, homophobia, anti-Semitism, anti-Islamism, anti-immigrantism, really all come from the same place--cowardice. In his history of lynching, Phillip Dray notes that mob violence against black men wasn't simply about keeping black men in their place--it was about keeping white women in their place. Lynching peaked as white women went to work outside the home in greater numbers, developing their own financial power base. White men, afraid that they couldn't compete with their women, would cowardly resort to lynching. I am not saying that the anti-gay marriage crowd is a lynch mob. But in tying opposition to the sexual revolution what you see is, beyond a fear of gay marriage, a fear for marriage itself. A fear that their way of life can't compete in these new times. It's ridiculous, of course. But bigotry always is.
DuBois wrote about racism as "the psychological wages of whiteness". Black equality would cost white people, and, of course, it did. You can't kill or rape blacks with impunity anymore, you can't make them sit in the back of the bus or stop them from drinking from 'your' fountain. So whites definitely lost things, both tangible and intangible, with the coming of equality. Of course, whites never had a right to those things. That's why the racial hierarchy had to be established, with all the attendant bennies and burdens nicely justified (whites are smart and work harder, etc.)
So, I think Coates is on to something with this notion - heteros lose one of the few advantages left to those born on the lucky side of any hierarchy, in this case, the sexuality continuum. Homophobes are manic about losing the right to have someone to openly look down on. To consider innately inferior. Which is convenient because their unworthiness then allows you to collect those psychological wages like straights only in the military, straights only in the classroom, straights only in public office (just imagine an openly gay Prez), straights only with the right to marry and all the bennies that come with it. Notice how quickly the psychological wages become all too tangible.
But this is an issue, like race, whose time has come. Enjoy the last few years left of discriminating against gays 'cuz them days is almost gone.
It's hard out there for a bigot. Homophobia is on a short list of acceptable bigotries. But it's fading fast.