When looking into the demographic breakdowns, via various news sites, it's not really surprising that the vote broke this way. I'm not trying to claim a bias based on race, just pointing out the facts. Obama generated a huge turn-out of voters who were not inclined to vote for same-sex marriages and also not inclined to restrict abortion any further. I had to double check because I just didn't see Prop 8 passing, and yet there is a direct cause and effect evident in the numbers: segments of the population with higher than normal turnout who overwhelmingly voted for Obama also voted No on 2 and Yes on 8. Specifically, black voters of both sexes, minority women, and self-identified regular churh attendees.
While there isn't much to be done about the church group, the efforts of those who support gay marriage should focus on education and outreach among the other sectors of the population that supported Prop.8 because just blaming the Mormons isn't going to change anything. Their efforts were marginally effective at best.