Same-sex Marriage will shortly be taken up by the US Supreme Court. I'll express my own legal opinion. If you're not prepared to read what I have to say then don't read further ~
My opinion is that if reason prevails, this will be the conclusive end of the ridiculous State-by-State, case-by-case lawsuits, and civil marriage -whatever you want to call it- will be fairly and equitably extended to all who meet the basic legal requirements. The reason has nothing at all to do with opinions about right and wrong, and everything to do with extending rights to a minority that have long been recognized by a majority.
Now, I'm sure that some will object based on their religious beliefs, interpretations of scripture, or other arguments. It is certainly your right, as a member of your church, to follow your own church's guidance and speak freely and as you wish. No freedoms of religion or expression are violated by others' private actions.
However, the first key legal point is that citizens of this country have had a separate and non-religious 'civil' pathway to marriage for many, many years. If the desire is to put marriage back into church, that would entail upending a very longstanding precedent. Not going to happen.
Yes, there are a [very] few countries that don't recognize civil marriage e.g. Saudi Arabia, Syria, Yemen...you get the picture. In these law-abiding United States, the issue is conclusively settled: you can get a civil marriage outside the church. Those wishing to marry are therefore not beholden to the strictures of any particular church.
It sends to me that the above point, alone, may not be quite sufficient to extend all same-sex marriage benefits, however. And so the second key point is that it would be unlawful to extend civil benefits in a way that discriminates on the basis of gender or race. This is perhaps not quite as legally enshrined as some might wish, but the spirit is well recognized throughout our legal system. You can't reward someone for being born as a particular gender or race; so too you can't penalize them.
Therefore, the right to civil marriage should ...and very certainly and inevitably.... will be extended to all who meet basic legal requirements e.g. age of consent and ability to recognize the terms and implications of the marriage contract. (And n.b. these latter qualifications very clearly exclude all the nonsense that some worry will turn us all to salt e.g. underage marriage, polygamy, unions between man and animal, and all the rest of the straw men typically offered!)
So, in conclusion, I say: the argument against same-sex marriage is already legally lost and that's the end of the story. We need to focus on far more important things than what consenting adults do in their own homes and whether they can share earned financial benefits.