The United States of America unanimously declared, "We hold these truths to be self-evident, that all men are created equal" in 1776. The 15th Amendment was ratified in 1920. It wasn't truly enforced until 45 years later with the Voting Rights Act of 1965. So why are we still fighting about giving everyone equal civil rights? Seems to me we covered that about 236 years ago.
If you are against marriage equality, think about this: How will another couple's marriage affect my life and my rights?
If you're worried about the sanctity of marriage, you should spend your time trying to criminalize divorce, as opposed to refusing the right to let more Americans enjoy the benefits of marriage.