DOMA violates the Tenth Amendment, which reserves the power for the states, by inserting the federal government for the first time in history into the definition of marriage. DOMA creates an untenable situation for a couples' children, their employers, creditors, businesses, government agencies, and others. Marriage is a powerful legal and social institution that protects and supports intimate family relationships by providing a unique set of rights, privileges and responsibilities. Most importantly, it's not just about sex. Anyone who is married knows that.
Marriage is an important personal choice and a basic human right.
The decision to marry should belong to the couple in love, not the state. Legally, religious and civil marriage are two separate institutions. Though many faiths do perform same-sex commitment ceremonies now, they have no legal recognition as civil marriage. Religions that do not approve of same-sex marriage would not be forced to perform them if they are recognized civilly. The state does not dictate which marriage any religion must perform or recognize, just as religions should not dictate who gets a civil marriage license from the state.