Traditional marriage as a social and religious institution is in question on several levels and a couple of legal definitions being examined by the Supreme Court. One issues it the Defense of Marriage Act which defines Marriage as between one man and one woman. The LGBT (Lesbian, Gay, Bisexual, and Transgender) community and their supporters would like Marriage to include same-sex marriage.
Domestic Partnerships is another alternative for LGBT couples but they are seeking equality, not equivalency. Many LGBT are also religious people who believe in Marriage just as heterosexuals do. Domestic Partnerships also make the law more redundant since they grant couple the same rights as marriage and any changes in law to one requires replication to the other. All forms and documents which only state Married must now say Married and/or Domestic Partner. This might also identifies couples as heterosexual or same-sex couples which might be an infringement on privacy. So there are good arguments against perpetuating both Marriages and Domestic Partnerships.
The reason for the controversy is that Christians feel that Marriage is a sacred lifetime union between one man and one woman. That had significance more than a hundred years ago but in today’s world marriages are often less than a lifetime. I fact many of our rich and famous marry one year, divorce the next and immediately marry again. It is not uncommon that a person marries more than 5 time. In states such as California the divorce rate is greater than 50% meaning that more than half of marriages fail. So the accepted practice of marriage and divorce has changed marriage significantly from its original religious intentions. Regardless of religious implications, in practice marriage is much more a legal state than a religious union. Thus those who insist that marriage is a religious institution do not reflect current practices.
The argument that marriage exists to offer a stable family unit through procreation is also not always practiced. There are heterosexual couples through choice or because of medical problems have no intentions of conceiving during marriage but still marry. This is acceptable under present practice and law so it is clear that the contemporary purpose of marriage is not for the sole purpose of raising a family.
So it is clear that the contemporary institution of Marriage has only vague resemblance to its historic and religious intentions. Religious conservative should fight to outlaw divorce and prohibit couples who have no intentions of having children from being married. The fact that they are not reveals that they have accepted the status quo that marriage is no longer a traditional religious institution but a legal status. This makes the LGBT claim that marriage should include same-sex unions that much more credible.
As in any civil rights movement the LGBT community will eventually be granted equal status and rights, not just equivalent status and rights and will become fully integrated into society. The myth that homosexuals are any more deviant in their behavior than heterosexual is starting to vanish. There is a lot of reprehensible heterosexual behavior tolerated by society that requires examination.
I would go even further about marriage. The word single should also be removed. There is ample evidence that humans are not monogamous. The fact that divorce is so common is ample proof of this. Even married couple commonly have extramarital affairs or solicit prostitutes for paid sex. There are many culture in the past and present which have been polygamous. There are Mormons who still secretly practice polygamy. The practice of Polygamy in Old Testament times by Jews was acceptable so there is nothing fundamental wrong with it. There is no evidence that children brought up on polygamous families turn out bad. As a matter of fact there is evidence that children from families with more than three siblings are very well-adjusted. Polygamous families often have many siblings. So I don’t see any reason for restricting marriage just between two people. To say conflicts with multiple spouses would cause more problems is no more supported than conflicts that routinely occurs between monogamous couples.
It is important to state how essential it is to maintain separation of Church from State. Legislating religious morality into law is always wrought with problems. Imposing Christian values on citizens who are not Christians is neither just, fair, nor equal.