According to the state, marriage is a legal contract that confers certain legal rights to a married couple, including property rights. (Divorce, therefore, becomes a matter for the court.) According to the church, marriage is a sacred union blessed by Jesus in the New Testament, one of the sacraments, like baptism. These two interpretations of marriage make the issue of gay marriage very complicated and frequently emotional.
Many of those who oppose gay marriage reject homosexuality as an aberration. Some view it as not only an unnatural state, but a sin, as well. Some politicians oppose gay marriage because endorsing it would mean the loss of political support.
The bedrock opposition to gay marriage represents the rejection of homosexuality. To accept homosexuality would require a major change in personal attitudes, and therein lies the current controversy. Some believe that homosexuality is an inherited biological condition; some believe it is a matter of choice. So, the issue of gay marriage is complicated not only by religious beliefs, but also by conflicting beliefs about the biology of homosexuality.
Gay marriage should be addressed as two issues, one civil and one religious. It is up to the church to decide whether or not to bless gay unions (and some churches do). For the state to deny a couple the right to enter into a civil contract, however, seems clearly discriminatory.
States should not issue "marriage" licenses to anyone; they should issue civil union contracts that would confer the same legal rights to every couple. Marriage licenses should be issued by churches. Taking the element of religious belief out of the controversy would simplify the issue tremendously for all--except for those who will continue to reject homosexuality as a sin. The rights one one individual, however, should not be trumped by the religious beliefs of another.