As a Unitarian Lay Pastor....
The Bible says exactly nothing about Gay Marriage and also very little about comittted loving same-sex relationships.
The Bible tells us that Homosexuality is a sin, t hat it is wrong...but it does not say why.
The writers of leviticus are concerned with defining the world. Judging and dividing the world based on their religious beliefs, into "Clean" and "unclean", that some animals, birds and marine life are clean and others arent. That some people and behaviours are clean and unclean. Animals with paws are ok but hooves are out; fish who look like fish are ok but jelly fish, shell fish etc are out. Birds who eat carrion are out. Its a totally logical but illogical list.
Surely this is saying to God that "hey, God. You go this wrong! Some of these animals are just wrong." Man usurping God?Man telling God his creation is wrong?
St Paul says Homosexual acts are unnatrual - "men given up to desires"...but doesnt say why it is unnatural. Furthermore, that is thinking from c.1800 years ago froma differant culture. St Paul also says it is wrong for women to have uncovered heads and men to have long hair. Remember he also says bankers and lawyers, like homosexuals, wont get into heaven.
The Bible doesnt not mention homosexuality becuse the word had not been invented.
The Bible doesnt say how people become homosexual.
The Bible doesnt say whether homosexuality is 'curable'.
The Bible doesnt tell us what kind of person is likelyto be a homosexual or about the quality of their relationships.
Most modern readers would agree with the Bible in rejecting:
Rape (e.g. at Sodom - rape not homosexuality in that story)
Intercourse with animals
However, most people tend to disagree with the Bible on:
intercourse during menstruation
naming sexual organs
being seen naked
celibacy (some texts)
exogamy (some texts)
considering semen and other body fluids as "unclean"
Simialrly the BIble also permits
sex with slaves
treatment of women as property
very young age for marriage
Whilst the Old Testament allows for divorce, Jesus specifically forbade it.
In short, we disagree more with the Bible on sexual mores than we agree with it. So why do Evangelicals turn to the Bible as a source of moral guidance and a de-facto statement on sexual behaviours such as homosexuality and ignore the Bible on others? I would suggest its hate, fear, personal dislike of homosexuality/uals and finding support for their dislike/hatred in scripture - picking and chosing what to believe just as they accuse liberals like me of doing.
The crux of the matter, for me is this: "Love your neighbour, love yourself, love God". Or as St Augustine said "Love God, and do as you please." Our moral task it so apply the Love Ethic of Jesus to all situations - to LOVE our enemies, to turn the other cheek,. To look at situation and find where the love is, to look where love can be applied and also critique the bible and all its thou shalt nots in the light of that love ehtic.