It's quite easy to scare someone into siding with you, especially when they were predisposed to agree with you anyway and you're merely giving them something to say to support their bigotry. There has always been a very clear and very prominent part of American culture (the 'freest' country on earth) that rejects anything which doesn't subscribe to the norm. And homosexuality isn't just different, many people feel repulsion to their very core when they even think about two men having sex. Note: The preconception is that it's always about sex, sex is dirty, it's easy to treat sex with disdain, it's far more difficult to argue away love.
And until homosexuality isn't viewed as outlandish and a challenge to the values which mainstream America holds dear, then there will always be people willing to stand up and proudly say that they support hatefulness and bigotry, especially when they delude themselves with things like 'it's for the children'. It's a culture war. North versus south, conservative versus liberal. It's just another thing that's been filtered into our increasingly polarized and politicized culture. Everyone loves to have an opponent, everyone loves a cause to fight for, and just like every other minority that has found a way to acceptance in American culture, we're going to have to fight like hell for it.
But let me get off my soap box and discuss Prop 8. My gut tells me that they are going to uphold it. It would be a very bold step to reverse a popular (although slimly) vote when a part of the backlash to begin with was that it was viewed as undemocratic that the judiciary took it upon itself to give out the right to marry to gays. If they were to argue that the Supreme Court, in striking down Virginia's anti-miscegenation statute in 1967 found that marriage was a basic civil right and cannot be taken away, they might be able to get away with it without too much backlash (which by the way, I think should be the argument when EVERYONE brings it up). But Rush, Hannity and all the other right-wing blabbermouths will still find ways to froth about it, of course.