Your article is plausible and perhaps a fair examination of one factor in the victory of Prop 8, but it patently avoids examination of one obvious non-Obama cause in order to flog its catchy thesis: There was an incredibly organized, well-funded, and powerful push by Catholics, Mormons, Southern Baptists, and non-affiliated evangelical "megachurches" to enlist their members in the pro-8 cause.
As a resident of one conservative Christian small town, and a school teacher in another fifty miles distant, I witness hundreds of corner picketers, a dozen or more sidewalk demonstrations, aand numerous churches with pro-Prop 8 signs. My students were abuzz with talk of their fervent passion for the concept of marriage between a man and a woman only. They tended to cite the (untrue) danger that their churches would be forced to perfom gay marriages under threat of lawsuit, and that schools would require that homosexuality would be taught as part of the curriculum. When I suggested that marriage for all was a civil rights or a privacy issue, students said yes, it was their right to religious freedom that was being abridged.
I have not run across a single African-American supporter of Prop. 8, nor have I seen any black pro-8 protesters. Of course, there are probably black members of the pro-8 congregations but in much of California, except for a few Baptist churches, the great majority of propagandizd and recruited Prop 8 proseltyzers would have been white Christians. And I believe their churches' money and bully pulpits and grass-roots organizing in Sunday schools and youth groups comprised a vastly more proximate cause of Prop 8's narrow victory than did blacks brought to the polls for Obama.