Christianity, (and religion in general), has the most to lose by this outrageous, twisted redefinition of marriage. Your thinking is shallow, and weak. What has always kept marriages together are the vows promised at the wedding ceremony, the children that need to be raised and cared for, the recognition that Jesus said marriage is indisolvable except for adultery, and the well known fact that marriage is the basic institution and the glue that holds together all civilized societies. Human "love" waxes and wanes and is as fickle as the weather, (witness the 52% divorce rate since the first attack on marriage that arrived under the banner of "no-fault divorce").
The ancient and modern purposes of marriage are to provide vows and a contract which help protect a betrothed man and woman from straying from each other, to maintain unity and cohesion, to protect the children of the marriage, and to provide basic rules and structure for the institution of marriage in a civilized society.
Any sexual relationship between two males or two females is nothing but a filthy, disgusting, debauchery of nature and of God's obvious plan for His creation to love and honor one another and to procreate the human species on earth. Any "marriage" of two homosexual perverts is not a marriage, nor will it ever be - regardless of what four liberal, pinko scumbags sitting on the Mass. Supreme Court may have invented.
I don't pretend to understand why two men such as those I met the other night live the life they either choose or through some act of biology have stumbled upon in their own life journeys. Like everyone else they will answer for their sins, their lifes good works will be rewarded, and they'll pay the price for judging others when that judgement is better left to the ultimate judge of all we do.
I'm not saying you shouldn't be disgusted, and I'm certainly not endorsing gay "marriage", I'm saying Jesus once took a prostitute in where his own followers were disgusted. That's the kind of Christian example that separates the old testament from the new.
Laying it all out there to be trampled by a half hearted civil rights crusade puts too much at risk with nothing to be gained. Fighting for school prayer, against abortion, or the 10 commandments makes more sense than denying these people a same sex union in the name of Chistian traditions. I say fight to keep them from calling it "marriage", and fight to keep the "basic rules and structure for the institution of marriage in a civilized society" the way it is.