A counter-argument can be made in very simple terms:
(1) Did Gay Marriage exist in Biblical days? Obviously no. Therefore the Bible could not be said to refute Gay Marriage, because Gay Marriage didn't then exist.
(2) All that existed in those days, was Gay fornication, adultery, servile pederasty, temple prostitution, and the like. All the Bible teachings are against these non-marital arrangements --- but not against Gay Marriage.
(3) The Old Testament prohibitions were man-on-man sex are just like the OT prohibitions on unclean (non-kosher) foods. Not applicable under the New Testament.
(4)The New Testament prohibitions were against pederasty, prostitution, and the like, not against marriage in any form.
(5) The Epistle to the Hebrews states: "Marriage is honorable in all, and the bed undefiled: but whoremongers and adulterers God will judge" (Hebrews 13:4). So marriage is honorable "to all" (not just heterosexuals) and it's only prostitution and adultery that makes it undefiled, not gay marriage.
Now I'm sure some FReepers will get on to argue as if I, Mrs. Don-o, were advocating these points: but I am not. I am completely anti- Gay Marriage, which is in itself a misnomer because the coupling of two people of the same sex is not even remotely analogous to marriage.
BUT my point is: it's really very easy to construct a pro-gay-marriage argument from Scripture Alone, --- if you don't buttress your argument with Natural Law and an agreed principle of authoritative interpretation.
I agree with you on all of these points but Jesus did define marriage.
"6 ...at the beginning of creation God 'made them male and female.’
7 ‘For this reason a man will leave his father and mother and be united to his wife,
8 and the two will become one flesh.’ So they are no longer two, but one flesh.
9 Therefore what God has joined together, let no one separate.”
The key here is in the translation, of which I am not an expert.* Did the original say, "who" God has joined together, which would point to a marriage based on the love of individuals for one another, or did the original say "what" God has joined together, which would indicate that male should be joined to female, and no one should "cast asunder" this institution of the natural order of things? My vote is for the latter; and I also believe that the Commandment "do not commit adultery" had a wide scope of application, not just sexual immorality, but any sort of deliberate adulteration of Truth, or of God's purposes in the created world.
Also, in Matthew 19:29 (NIV), Jesus said, "And everyone who has left houses or brothers or sisters or father or mother or wife or children or fields for my sake will receive a hundred times as much and will inherit eternal life." Throughout the Bible he refers to persons in terms of their sex. He does not say "siblings", but "brothers or sisters". He does not say "parents", but "father or mother"; and he does not say "spouse" or "partner", but "wife", having already covered elsewhere that men are to be the caretakers of women and children and love them as God himself loves the Church. The only non-specific sex in this passage is "children", not because their sex did not matter, but because they are all dependents of the adults not just for their upbringing, but also for the social order in which they live and which they will inherit.
*wideawake, you know Bible scholarship. What do you say?