Anyone who thinks that finding out what the Bible really teaches about same-sex love will resolve the issues for churches and individual believers misunderstands how things work in the real world. What the Bible really teaches is a function of somebody's interpretation. As my country relatives in Georgia used to say, "You can prove anything by the Bible."
A more humane view of gay marriage and its attendant issues will come like the resolution of African slavery, the right of women to vote, segregation, and the role of women in the church. It will come as a result of a change of consciousness in the secular culture and in the minds of Christians.
Slavery, the denial of women's rights, and segregation were all once defended on biblical grounds by wide segments of the Christan world, including biblical scholars, theologians, and lay people. They are not any more because the Christian community came to recognize that what they had been defending and supporting was wrong, and accordingly exegesis now easily produces a different result aided by hermeneutical miracles that are always available when needed.
Christians never let the Bible when it is speaking as the Word of God support or condone what is known or strongly believed to be either untrue or immoral. Check it out in church history.
The same pattern will repeat itself with regard to same-sex love. Southern Baptists apologized some years ago for defending segregation. Bob Jones University has decided its ban on interracial dating was a matter of culture and not a scriptural mandate. Nobody today thinks the Bible supports slavery.
With regard to homosexuality we are now where we were with slavery in 1850 and segregation in 1950. Biblical scholars at the moment divide sharply on the question of whether the Bible forbids and condemns same-sex love as immoral. In a half-century, I predict the exegetical, ecclesiastical, and theological worlds will sing a different tune. The Roman Catholic hierarchy moves at its own pace, but eventually will come around as it did on Galileo, evolution, democracy, separation of church and state, and other things.
Meanwhile, in the secular and political world change is coming slowly, and it is coming generationally, geographically, racially, ethnically and in terms of social and cultural location. New New England led the way, and California and New York are moving along. The upper Midwest could be next. The South, Midwest, Plains and Mountain States will follow in time.
Many highly-educated whites in the knowledge and professional classes are further along than many African Americans and Hispanics, especially the more religious ones, although education, culture, and class matter here too.
In the meantime, it you wish to gauge the opinion of Christians ask first not about their church membership but about their zip code.
When all the nuances, qualifications, and caveats are added, I will stand by the claims herein.