Answer:
Conservative Christians believe that marriage is a sacred religious sacrament ordained by God between a man and a woman. They believe that same sex relationships are against God's will. There is nothing wrong about that belief as long as it stays within the walls of the church. However, religionists have always sought to transform their personal and religious beliefs into civil law.
Marriage is actually a legal civil arrangement that carries with it a host of legal rights. The government is under no obligation to reflect anyone's religious beliefs in civil laws. In the United States clergy are among the many officials who are permitted by the government to perform marriage ceremonies. However, without a civil marriage license the marriage is not legal. Many same sex couples have a life long committed relationship and where same sex marriage is not recognized they are denied those legal rights that long term committed heterosexuals can acquire through marriage.