(and not exactly supported by Christian scripture, either)
It's not quite the hot-button topic it used to be, but the idea of two people of the same sex entering into marriage with each other is still something that can polarize groups pretty quickly. For some reason, some people really like the idea of the government, federal or local, defining the institution of marriage for them; they actually want to invite politicians into this important and ideally sacred aspect of human existence. I'm not one of those people.
Though we frequently fail to live up to it, our country is founded on ideals of equality and liberty. That doesn't mean everyone is equal, nor that everyone is free to do whatever they want. Rather, we should strive to create a government that will treat all citizens as citizens, one that turns a more blind eye than it does to individuals' religious beliefs, skin colors, socioeconomic status, and similar conditions- i.e., people who have seven-figure incomes should be just as liable for their crimes as people who qualify for the Earned Income Tax Credit. Legally allowing homosexual couples to form marriages is not "special treatment"; it's equal treatment (I suspect people who denounce such "special treatment" for some reason envy the openly homosexual; perhaps these denouncers are closet homosexuals themselves and are angry that they've lived false lives as heterosexuals).
If we accept marriage as a religious covenant, then the state has no business defining it. Similarly, if marriage is instead a civil contract, then no religion has any earthly authority over the definition, and to restrict people from entering into the contract based on something like sexual preference runs contrary to the laws and principles of the United States of America.
Personally, I think marriage is something that far too many people enter into. If someone really wants to do it, though, I'm not going to stop them. Laws regarding who's allowed to marry whom have changed through our country's history. It was only after the civil war that African Americans were allowed to marry in all areas of the U.S., and it was only after a U.S. Supreme Court decision in 1967, Loving vs. Virginia, that mixed race couples could marry anywhere in the U.S. The arguments against allowing them to marry were much the same as the arguments made today against allowing same-sex marriages to occur. Allowing "civil unions" but not marriages is pretty awful, too. Could you imagine a politician in our day saying something like "I support the right of African Americans to form civil unions, but I don't think they should be able to call it marriage"?
It's not as though other cultures in the past haven't had same-sex arrangements. Finds such as the tomb of two males, Niankhkhnum and Khnumhotep, in which the two were buried in the same manner as husband and wife, likely indicate that same-sex unions in ancient Egypt were recognized as marriages. Same-sex unions (usually involving pederasty) were an integral part of the cultures of classical Greece and republican and imperial Rome. Many African tribes have recognized lesbian marriages, and among the Azande of the Congo males would sometimes marry other males (and pay those males' fathers a bride price, especially when those males were youths) before the arrival of Christian missionaries. Some Native American tribes opened marriage to same-sex couples, again before the arrival of Christian missionaries.
As far as stances against same-sex marriage is a based upon interpretations of the Christian Bible, well, I would like to point out the following: Many popular English translations of the Bible are far more homophobic in their language than their Greek and Hebrew counterparts. Of ones I've read, in particular the Living Bible is bad; it even translates instances in which Old Testament men kiss each other in greeting or farewell as them instead shaking hands. Though there isn't any evidence of them engaging in crazy homosexual sex in their relationships, David, Ruth, and Daniel all had loving same-sex relationships (with Jonathan, Naomi, and Ashpenaz, respectively).
According to the Ontario Council on Religious Tolerance, many passages quoted by homophobic "Christians" as being condemning of homosexuality don't necessarily condemn homosexuality per se. Rather, the passages can be interpreted as condemning more bizarre or evil acts; some instead interpret these passages as condemning:
-Homosexual rape (Genesis 19; Judges 19:14).
-Homosexual ritual sex in Pagan temples (Leviticus 18:22 and Leviticus 20:13).
-Homosexual prostitution (Deuteronomy 23:17; 1 Kings 14:24, 15:12, 22:46; 2 Kings 23:7).
-Heterosexual men and women going against their basic nature and engaging in homosexual Pagan orgies (Romans 1:26).
-Men who sexually molest boys (and the boys that they abuse) (1 Corinthians 6:9; 1 Timothy 1:9).
-Bestiality: Men engaging in sex with males of another species, angels in this case (Jude 7).
There is absolutely no mention, from Genesis to Revelation, of same-sex marriage. None. I defy anyone to produce a passage from the Bible condemning same-sex marriage. Not some ambiguous passage that may condemn some of the behavior that you might expect homosexual couples to display (I know of at least a few married couples who don't have sex), but a passage in which God says something along the lines of "same-sex marriage is an abomination."
Currently, the Netherlands, Belgium, Spain, Canada, and South Africa (taking effect December 2006) recognize same-sex marriages. It's true that the United States all too often lags behind the rest of the world in granting equality and freedom to its citizens (it took us until the 1860s and we had to fight a civil war before slavery finally came to an end, and it wasn't until a hundred years after that that we had the Civil Rights Movement), but perhaps the actions of such countries will help closet homosexuals denouncing special treatment and others like them see that legally opposing the rights of homosexuals to marry is unpatriotic and un-Christian.
Resources:
Chauncey, George. Why Marriage? (2004)
Marx, Anthony. Making Race and Nation: A Comparison of the United States, South Africa (1998)
Matthews, J. Scott. "The political foundations of support for same-sex marriage in Canada" at: http://www.cpsa-acsp.ca/
McCoy, John. "Evidence of Gay Relationships Exists as Early as 2400 B.C." The Dallas Morning News (July 20, 1998)
Ontario Consultants for Religious Tolerance. "Homosexual (Same-Sex) Marriages- All Sides to the Issue" at http://www.religioustolerance.org/hom_marr_menu.htm