There is much that has been written explaining how same-sex "marriage" is wrong morally, philosophically, socially, and so on.
Here is my two cents on "A Bronx Cheer for Real Marriage" (Worldmag.com, May 18, 2011).
Advocates of the change present same-sex marriage as a civil rights issue. They ask, if you can, why can’t we? ...
But there’s a problem. It’s not marriage. As I enjoyed my first and perhaps final stroll through the Bronx, I searched for a plausible analogy and settled on another unique human relationship: the church. In our society, churches have certain tax advantages over other organizations and a respectability that not every organization has. What homosexuals want is comparable to insurance companies demanding that they too be recognized as churches. This would improve their public image and their bottom line at the same time. There is a surface resemblance, no? Like churches, they have buildings, they bring in money, and they take care of people.
But there’s a problem. They are not churches. There is something essential to a church that does not and cannot happen in an insurance company as an insurance company, namely the worship of God. So, too, there is something essential to marriage that does not and cannot happen in an intimate, homosexual friendship, namely reproduction. Granted, there are heterosexual couples who cannot have children. But that is an accident of nature. In homosexual couples, it is a principle of nature.
I will have a fuller argument in my forthcoming book, Left, Right, and Christ: Evangelical Faith in Politics, which I co-author with Lisa Sharon Harper who argues in favor of this novel arrangement. Russell Media will publish it in October.
Worth reading on the subject:
Esolen, Anthony. “A Requiem for Friendship: Why Boys Will Not Be Boys & Other Consequences of the Sexual Revolution,” Touchstone, September 2005.
_____________. “Same-Sex Marriage: Anthony Esolen’s Ten Arguments for Sanity,” Touchstone Magazine: Mere Comments, January 25, 2010.
Shell, Susan M. “The Liberal Case Against Gay Marriage,” The Public Interest, Summer 2004.
Tubbs, David L. Freedom's Orphans: Contemporary Liberalism and the Fate of American Children (Princeton: Princeton University Press, 2007).
Tubbs, David L. and Robert P. George, "Redefining Marriage Away," City Journal, Summer 2004.