Same-sex "marriage" makes sense if. . .

Michael Horton:

 If God exists for our happiness and self-fulfillment, validating our sovereign right to choose our identity, then opposition to same-sex marriage (or abortion) is just irrational prejudice.

Given the broader worldview that many Americans (including Christians) embrace—or at least assume, same-sex marriage is a right to which anyone is legally entitled. After all, traditional marriages in our society are largely treated as contractual rather than covenantal, means of mutual self-fulfillment more than serving a larger purpose ordained by God. The state of the traditional family is so precarious that one wonders how same-sex marriage can appreciably deprave it.

Same-sex marriage makes sense if you assume that the individual is the center of the universe, that God—if he exists—is there to make us happy, and that our choices are not grounded in a nature created by God but in arbitrary self-construction. To the extent that this sort of “moralistic-therapeutic-deism” prevails in our churches, can we expect the world to think any differently? If we treat God as a product we sell to consumers for their self-improvement programs and make personal choice the trigger of salvation itself, then it may come as a big surprise (even contradiction) to the world when we tell them that truth (the way things are) trumps feelings and personal choice (what we want to make things to be).

 More here.