Here's a Hot Air post on a Gallup poll to that effect. Notice this line in the post:
"It may be that, even among GOP skeptics of gay marriage, the normalization of gays in the media over the past 15 years has caused their moral opinions of homosexuality to change if not their belief that marriage, as a religious institution, should remain one for heterosexual couples only."
There it is: "in the media". Poor time management is a major problem in cultures like the United States. It's worse than abortion, neglect of the poor, and other moral problems people often cite when asked what's wrong with a culture. Americans spend far too much time on trivial and vulgar television programs and movies, following sports, and the like. Their priorities are desperately wrong, and their time management is awful. Click on the Time Management label at the end of this post, and you can see an archive of posts I've written on the subject. I've cited a lot of polling data and other research that's been done. One of the reasons why parents, pastors, teachers, and other people in such positions of influence don't adequately address the problem with time management is that so many of them are a significant part of the problem.
Hot Air also has a post on how most Americans think that at least 20% of the population is homosexual. Where did they get that idea? Largely from the media they spend too much time with. The Hot Air post refers to "visibility in celebrity culture" and how "gays and gay-rights issues seem to be everywhere in media and on the news". Why are people following celebrity culture and depending on the mainstream media so much to begin with? And why didn't their misconceptions about homosexuality get corrected by more accurate sources they were spending time with? Because they aren't spending much time with more accurate sources. Even if they were, they probably wouldn't want to spend the time needed to do further research, think through the issues sufficiently, etc. Americans have more important things to do with their time, like watching sitcoms, going to baseball games, doing unnecessary housework, and reading romance novels.