I would probably be better off if I didn't participate, but I suppose I'm one of the few that will openly discuss it from this perspective.
The reasoning is underpinned largely by the concept that in our cultural history marriage was defined as "starting a family". Children deserved to be raise by their biological parents. If that wasn't possible, they deserved to be raised in the best situation possible.
Prior to widespread birth control and abortion, people were strongly discouraged from having sex prior to marriage primarily due to the risk of pregnancy and creating a child which would have no strong family unit which would care for it until adulthood. However, society has changed drastically since then. With birth control and abortion we've dropped to the lowest birth rate on record:
http://www.washingtonpost.com/blogs...t-ii-u-s-birthrate-falls-to-lowest-on-record/
In fact it turns out that if we didn't have so much immigration, both legal and illegal, we'd be in the same position today as many Asian and some European countries are - too many old people, not enough young people. I'm only pointing this out to indicate that the birthrate would be far lower without immigration, and the graph isn't telling the whole story.
We have evidence that shows children raised in a heterosexual parented house do well, and generally end up contributing members of society.
Right now we don't have much in the way of studies, especially long term studies, regarding children raised in homosexual parented houses. These studies are ongoing, many states allow domestic partners to adopt children, and eventually those studies will show whether this is as good as a heterosexual parented family or not.
Further, those children need to have a reasonable safety net and path of inheritance in case something happens to one or both parents. Thus marriage defines what happens to property upon death. When one parent dies, the property goes to the other parent, and/or to the children - in full consideration of the children. These laws were not designed with the idea that the widow or widower would get the full control of the property for his benefit, but for the benefit of his children.
Marriage was not about finding your life partner, sharing your property with each other, and making decisions for each other when the other is incapacitated. Marriage was about marrying your life partner for the purpose of bringing children into the world and providing a safe stable learning environment where they can then contribute to society as adults.
This started to change with birth control, abortion, and free love, where people were instead encouraged to turn inward to their own needs and desires, and choose families and children as a possible choice out of hundreds, rather than a societal expectation.
Now we have come to another turning point in how our society defines marriage.
Society has a direct interest in making sure children are raised to become productive adults in society, and in growing our society. Right now we know, through long term studies, that children of a single father or a single mother are at a disadvantage when compared to children raised in a home with both a mother and a father. This is not to imply they are better or worse, or that they didn't turn out as good as they could have. Simply that studies show they have fewer opportunities in life to grow and learn comparatively.
The key question is:
Does this difference hinge on the number of parents, or on the dual representation of the sexes as parents?
In other words, are children of a two male parenting or two female parenting at any disadvantage compared to a male/female parenting situation. We don't have the studies that prove either way, and short term studies are going in both directions, seemingly based on who funded them.
So, do we jump in with both feet and allow this redefinition of marriage without enough information on how it will alter society in the long run, or do we wait for a few more decades to find out how the experiments going on in a dozen states and with tens of thousands of children turn out?
I say we wait.
Others say we shouldn't (or, alternately, they point to one or two short term studies that back them up and say "that's enough information, let's go")
That is, insofar as I can tell, the only logical basis for discriminating against LGBT individuals. Every other form of discrimination (job, health, housing, etc) has no excuse, those forms of LGBT discrimination should be done away with.
But marriage is a special case that may directly depend on the constitution of the marriage, and may directly impact society, and this impact may be negative. We should carefully consider and balance the discrimination against society's need for encouraging the best family situation for bringing children into society.
