Government has no place dictating matters of faith
If people are against same-sex marriage, then they ought not enter into one, but that’s where their authority ends. No one, including the government, has or ought to have authority over the rights and actions of others that harm no one else – that’s a fundamental tenet of this country’s founding principles and part of the definition of the rights of its people.
The argument that gay marriage will ruin the institution of marriage itself infers that a happily married couple of many years will find their marriage ruined if the cohabiting guys down the street get married. This is ridiculous on its face.
The government’s role in marriage ought to be to define its legal terms only, recognizing it as a form of secular contract between individuals in the same legal arena as any other business contract. That is appropriate for marriage since a large part of what it includes are secular commitments and obligations devoid of reference to faith.
If some need or want to have a religious connotation added to make it complete, they are free to do so. If their religion won’t bless some sorts of marriage and that’s a deal breaker for them, that’s their choice based on faith. But the limits of one faith ought not limit others of different (or no) faith. The government has no place in matters of faith or its absence.