"You can be gay and Muslim."
It would seem that marriage is some form of societal construct that allows for two individuals to create some type of life partnership and, in a gestalt manner, to be legally recognized as such. The result is that in an array of legal matters -- from taxation to insurance to inheritance -- these individuals are now perceived within the rules of this partnership.
The reality is that society saw in the marital unit a structure that was beneficial to society, for one reason or another, and so it responded accordingly. The fact is, though, that changes in society have made marriage irrelevant in regard to those original benefits to society.
I was recently invited to debate Pastor Ted Haggard regarding whether a state should allow same-sex marriages or not. To me, the issue of same-sex marriage is not one of individual rights but, rather, involves the fine and detailed structure of society. The marital unit is the building block of society and its re-classification to include the same-sex couple is not just a matter of a simple change of definition.