This was the question put out by Charlie Bucher & his morning crew on AM 1190 (WOWO - Ft. Wayne) during their "Morning News & Views" segment. At least four people, maybe five, all sputtered and stuttered their way to tip-toe through such a "sensitive" topic. Of course, this "news story" is driven by the decision by the California courts to legalize and recognize "gay" marriage. It is an interesting question. However, I was surprised at the hesitancy of the news crew to address the issue straightforth. Comments varied but were along the lines of: marriage is for those who love each other, homosexuals can't help themselves because they're born that way - so they ought to be able to enjoy marriage, marriage is a religious and social thing because it's been that way for a "bazillion" years, etc, etc.
It is very simple to answer the question of whether marriage is a religious instituion or social construct. But to answer it will depend on your view of God's Word. If you believe it to be the authoritative book that has everything pertaining to life and Godliness, then the question is readily answered. Until you hold that view, you will struggle with being politically correct and speaking at the risk of offense. I hold the former view. I believe God's Word is the authoritative rule in my life. If I struggle with what it says, I struggle with God. If I come to a moment when I must choose between my thoughts on an issue or God's thoughts on an issue - I must choose God's thoughts and ways.
Marriage is an institution set up by God, ordained by Him at the time of the creation of Adam and Eve. It is not an issue of "Law", or man's construct. Moses didn't come up with marriage - God did. God's sacred plan for mankind is that a man leave mother and father and cleave to his wife, becoming one flesh. This isn't just God condoning a sexual union. One flesh goes much farther than that. Thus we see God's boundaries for marriage. One man - one woman - intimacy apart from all others. In the entirity of Scripture we see marriage fleshed out as the Holy Spirit revealed more through the writers of His Word.
I see marriage concisely defined well in the Westminster Confession of Faith, from which I partially quote: "...Marriage was ordained for the mutual help of husband and wife, for the increase of mankind with a legitimate issue, and of the Church with an holy seed; and for the preventing of uncleanness (sexual impropriety, including, but not limited to homosexuality)..."
Marriage is not a social construct. It is an institution ordained by God, initiated by God and held in sacred esteem by God. To distort it is to defiantly fly in the face of a Holy God. There is no other option for mankind to consider - it does not matter what the courts of this land may say - God has given us His best for us in the text of Scripture. To follow it is to ensure joy, peace and happiness as promised by Jesus Christ. To disobey is to invite the wrath of the Almighty.