This is an interesting debate question.
Currently, this is a debate that is ongoing in several states. Opponents of gay marriage argue that there is a strong government interest in preserving the traditional family. The extension of this argument is that gay marriage would degrade family values and break down the importance of the traditional family.
Supporters of gay marriage argue that this is a myth.
In fact, the traditional family has evolved over the years. It’s hard to define the traditional family in modern times. Are we talking about mom and dad and the kids, or is it mom, dad, step-mom, step-dad, and the half brothers and sisters. It’s arguable that if allowed to marry, gay couples may cherish their hard won rights, resulting in a lower divorce rate amongst gay couples.
Opponents of gay marriage also point out that gay couples can avail themselves to a civil union which carries all the same rights as marriage. This is an interesting argument that certainly cuts both ways. If marriage and civil union are the same thing, then the same argument can be used to argue on behalf of legalizing marriage for gay couples. What’s the difference, if it truly is the same thing. Consider the flip side for heterosexual couples. Calling my wife a civil partner just doesn’t have the same ring.
Philosophy aside, what is a state’s interest in marriage? Traditional marriage was invented in religion, however the government also has a legitimate interest in recognizing marriage in the law. The government interest in marriage is fundamentally in recognizing the property interest between a married couple. Without the legal recognition of marriage, the succession of property becomes problematic when someone passes away. Consider a non-married couple with a child born out of wedlock. If the father of the child passes away, the mother of the child would not be entitled to any property from the father. The minor child would likely inherit. However, if the couple were married, then the wife would have a property interest.
The government should have a strong interest in legitimizing these property rights amongst all couples who wish to tie the proverbial knot.
Lastly, consider the equal protection arguments. If there’s no argument against allowing a legal civil union, which supposedly carries all the same rights as marriage, then why single out a single group of people to say that they can’t use the word marriage to describe their union?