I have the misfortune of having to be around many Conservative Southern Baptists more than I'd prefer.
I can tell you how they view same sex marriage, because I have heard it a million times.
There is this thing called mission creep, and they've used that to coin their own phrase called "definition creep". To them, this means changing the original definition of a word.
So to them, the term marriage is suffering from definition creep. It's meaning is changing, and it shouldn't. They think it should be called a new word, because marriage is for a MAN and WOMAN, and not for two people of the same gender. They want a new word created to refer to that type of union. They aren't really against there being some sort of union or legal partnership that allows for them to share health benefits, or stay at the hospital during visiting hours, or be the recipient of whatever is left to them upon death, etc.
They view it as something similar to all of a sudden, Hooters letting men be waiters, and wearing the same short orange shorts and tight tank top. It's always been only for women, so it should always be like that!! Don't give the job description job description creep!!
None of them have really arrived at these views and opinions themselves. It's just what they hear propagated around in their church services, families, communities, etc. It's just spewed ignorance, over and over, and it spreads. Just like the little kid who said he would have burned that pilot if he had been given the chance. You can warp the mind and teach a child anything. They only know what they are taught. I believed in Santa and the Easter bunny until I figured out/was told that they weren't real. I also believed in God and Jesus and all of that Sunday school nonsense until middle school, when I began to think for myself and realize that it all seemed very silly to me. It's shocking to me how adults with the ability to think rationally have these beliefs, and it's even more shocking to me when they use these beliefs to oppress people with a different sexual orientation.