This chart was made from the 2014 survey of 40,000 Americans during 2014 by the Public Religion Research Institute -- and it will probably come as a shock to many of the religious bigots in this country. It turns out that they are a small and diminishing minority in the United States, even among the religious. Most religious (and non-religious) Americans support the legalization of same-sex marriage.
I list the 16 major religious groups in the United States in the chart above. It turns out that only 6 of those groups don't have majority support for legalizing same-sex marriage, and even those groups have many supporting it -- including over a fourth of evangelicals and mormons, more than a third of Black and Hispanic protestants, and more than four out of 10 muslims.
The majorities in those 6 groups want Americans to think they represent religious thought in this country, and that most religious people agree with them. But that simply is not true -- and they should have learned that from the recent outrage over the bigoted "religious freedom" laws they have tried to pass (which have nothing to do with religious freedom, and everything to do with trying to establish an unconstitutional right to discriminate).
The other 10 religious groups in the United States (accounting for most American citizens) all have at least 55% of their membership support same-sex marriage. That support ranges from 55% to 94%. Clearly, the bigots do not speak for most Americans, most religious people, or even most christians.