So how is stopping two people of the same sex from being married any different from stopping a man and his adult daughter from being married? On what grounds would you allow one over the other?
And, if you plan to argue the whole birth-defect point, what if one is incapable of having children? Is it OK then?
"So how is stopping two people of the same sex from being married any different from stopping a man and his adult daughter from being married? On what grounds would you allow one over the other?"
Because government sanctioned marriage is an endorsement and an incentive. We don't endorse most things just because they are allowed -it two different questions. I'm allowed to over eat, be lazy and not go to church but I don't want the government encouraging those things either.