I am not sure how you are determining the big outreach of churches or even assuming they act as one ... there are churches in the US (a minority, but they do exist that allow gay pastors) .... People attending church (not that I really think there is anything wrong with people that do) is on the decline in the US.
Also, for the conservative point, it is worth noting that the last (so far as I know) gay marriage ban passed by voters happened in California in 2008 when masses were out to vote for Obama, many members of his coalition was voting to ban gay marriage. Exit polls show the largest groups voting in favor of the ban (in order) were Blacks, Latinos, Asians, "other", White.
Poorer people favored the ban more, but younger people were opposed to it. All of which leads to the conclusion that while religion is certainly a factor, racial identity (in the case of blacks, I do not think they want to share the Civil Rights podium with anyone along with religion), and as time goes on (ie old people die), support will increase.
All of this indicates a population that is more and more favoring of gays and pending some massive event will continue to be so despite any church influences.
Yes on Prop 8 means being in favor of a gay marriage ban.
http://www.madpickles.org/California_Proposition_8.html
Race
Looking at the vote by race reveals a curious detail:
Race % of respondents Yes on prop 8 No on prop 8
White (63%) 49% 51%
African-American (10%) 70% 30%
Latino (18%) 53% 47%
Asian (6%) 49% 51%
Other (3%) 51% 49%
That data can be reduced to:
Race % of respondents Yes on prop 8 No on prop 8
African-American (10%) 70% 30%
Other (90%) 50% 50%
Poorer people also favored the ban
Vote by Income % of respondents Yes on prop 8 No on prop 8
Under $15,000 (5%) 46% 54%
$15-30,000 (10%) 48% 52%
$30-50,000 (15%) 54% 46%
$50-75,000 (19%) 54% 46%
$75-100,000 (17%) 50% 50%
$100-150,000 (17%) 54% 46%
$150-200,000 (7%) 47% 53%
$200,000 or More (9%) 45% 55%
Vote by Age % of respondents Yes on prop 8 No on prop 8
18-24 (11%) 34% 66%
25-29 (9%) 39% 61%
30-39 (17%) 50% 50%
40-49 (22%) 57% 43%
50-64 (26%) 51% 49%
65 or Over (15%) 61% 39%