If you strip away the moral standard and religious righteousness of gay marriage, you boil down the issues to one simple norm, that being social justice.
Members of the gay community work, live and die in our communities like everyone else and should be given equal social rights and privileges in their long-term relationships from a legal standpoint.
They pay taxes, contribute to the common good and in all parts are equal members of our society.
So the only focus from our government should be social equality.
When we mix one's morality and religion, the issues become more dogmatic and blurry. Perhaps this is the real reason and utility for a separation of church and state.
To use the Bible as a reference in this issue of gay marriage is similar to using the constitution for lack of gun control.
Each only stagnates the message intended by the designer and does not allow for an update and a living version of its teachings and directives.
By the way, I am not gay and I am a Christian, and the teachings of our Lord demand social justice by the commandment to "Love thy neighbor as yourself."