Legislators are mostly about telling people what to do. And in our republic we call on legislators to influence--often to control--the actions of fellow citizens. But we also live by principles, so that the considerable demands we make on others are not expressions of prejudice, mere whim, or the worst of our impulses.
There are several arguments against same-sex marriage, but for the most part, the counter-arguments are better.
A few people argue that the institution of marriage for homosexuals would weaken the appeal of heterosexual marriage by making the latter a less privileged arrangement. They claim that marriage for homosexuals might also reduce the respect that people have for the institution of heterosexual marriage. That is unmitigated poppycock.
Same-sex marriages do not undermine heterosexual marriages: They will not prompt heterosexual partners to feel that their unions are devalued. They will not lead married people to get divorces because they feel that the institution of marriage is sullied. They will not reduce the number of people seeking to get married. They will not undermine the bonds of matrimony anywhere at any time for any reason (although there are plenty of other forces at work on that).
Some authors, particularly Andrew Sullivan, have advanced good conservative arguments in favor of same-sex marriage. He wrote that "Like straight marriage," gay marriage "would foster social cohesion, emotional security, and economic prudence." He also argued that the institution of marriage for homosexuals would confirm the existence of relationships and thereby help to determine rights and responsibilities for the partners. Furthermore, same-sex marriage would tend to reduce promiscuity and thereby help to limit the spread of sexually transmitted diseases. (Sullivan)
The recent ruling of U. S. District Judge Vaughn Walker against Proposition 8, which banned same-sex marriage in California, is a move in the right direction. But among the States, the legislation on this matter is a patchwork, and the basic rights that American citizens have in this regard are neither uniform nor clear. The Supreme Court could help to settle this issue, although whatever the decision, a great many people will not like it.
Recognition of same-sex marriage will make an economic impact: many employers, insurance companies, and agencies of government will have extra costs, for example, health and insurance benefits, and paid leave for caregiving. Financial adjustments will have to occur to accommodate new beneficiaries. And yet, these effects do not warrant any opposition to the principle of same-sex marriage.
Laws will not--certainly ought not to--force clerics, in violation of their beliefs, to perform same-sex marriages. Laws that grant civil liberties to gays and lesbians will not--certainly ought not to--force changes in the practices of religious institutions that prohibit homosexual marriages.
The main question here is whether one group of people can establish laws to force another group to conform to a set of beliefs, when those laws aim only at producing conformity and not at preventing harm. Some actions, like theft, rape and murder, are clearly harmful to society. Appropriately, laws prohibit them. But no harm to civil society is created by same-sex marriage.
For the most part, the fundamental motivation for anti-gay and anti-lesbian laws is an offense on sensibilities or the notion that homosexuality is a sin. Laws need not be and ought not to be passed to prevent others from committing 'sin' when 'sin' (while it may harm the sinner) does no harm to society. Fears that, if others are allowed to sin, God will punish the innocent who happen to reside in vicinities where sins are committed are preposterous and ought to be dispelled.
Too often, the only reason that we deny rights to other people is that we regard them as 'different' from us. The degree to which we see people as having the same aspirations, the same concerns, the same fears and vulnerabilities is the degree to which we are likely to grant them the same rights. Whether those other people--'different' from ourselves--have the same rights that we enjoy, or be denied them, may make no difference in our lives. Nevertheless, it can make a very big difference in theirs.
Reference
Andrew Sullivan, "Here Comes the Groom", New Republic, August 28, 1989.