It's funny how Christians are often accused of trying to 'deny' gay people the 'right' to marry (when really no such right exists and it's something for society to decide in the scheme of things). At least the adults in the discussion have the opportunity to argue their case.
On the other hand, creating a structure where a child (who has no opportunity to argue their own case) is explicitly and by design denied the opportunity to be raised by it's biological parents is no problem for the SSM advocates. It doesn't matter that we can point to any number of adopted people who wonder who their birth parents were even if these people still do well in life and tick the various boxes of 'no different than if they weren't adopted'. The fact that part of their story remains unknown is often a source of constant wonder and often sadness. Now adoption is an example where we make the best of a bad deal and often times that can be an awesome outcome anyway even if it's not the way we'd prefer it to be.
So the question is do you think a child has the right to be raised by it's mother and father? Or do you instead suggest that the child has no rights in this situation and it's rights are whatever happens to be defined by the whims of those who 'want a child'?
Please don't go down the road of 'some heterosexual parents are crap' because we can also point to some same sex parents being crap too- including a high profile QLD case. When parents are crap society makes the best of a bad deal and we ensure the kids are safe. That's not the point I'm talking about here and everyone knows it so I'm hoping we can head that off at the pass.