On Gay Marriage: I recommend reading "Justice and Social Order" by Emil Brunner. This brings to bear reasoning between Absolute & Positive Justice. Man, in his humanness, is unable to fulfill absolute justice but can and does render positive justice [to each his own]. However, in formulating state statues governing man, the precepts of positive justice should not fall to the 2nd or 3rd choices below the Absolute.
Justice in the Political Order - "...every man owes his creaturely existence to the fact that two individuals, a man and a woman, became one...and every [person], at the root of his existence is part of a community. This community, however, is not the State, but the family: the one community without which there would be no State. Hence, it is the Family, not the State, which is the primal community and it rights, by the order of creation, are primal. The State is only just when its legal system lays due stress on the law of marriage and the family, which are independent of it."