Nineteen years ago, then-San Francisco Mayor Gavin Newsom sanctioned same-sex marriages. As mayor of San Francisco both a city and a county he had the authority to perform marriages, though not same-sex ones. That didnt matter.

We didnt have the formal authority, he once told me in an interview several years ago, but I felt we had a moral authority to challenge the law.

Back then, same-sex marriage was illegal across the country except in Massachusetts. It would become legal in California that June. Newsoms move ignited legal challenges, ballot propositions and a national debate intended to settle the issue once and for all.

Many criticized Newsom both for the marriages he sanctioned in San Francisco and for his brazen 2008 prediction that same-sex marriage was gonna happen, whether ya like it or not. His actions galvanized opponents and became an effective fear-mongering tic for Proposition 8, Californias anti-gay marriage initiative.

But in the end, Newsom was right: same-sex marriage won, eventually becoming legal in all 50 states.

And conservatives were wrong. Unlike Newsom, their spasmodic predictions never came to pass. Traditional marriage survived, and continues to thrive. Society didnt collapse into Roman Empire-like debauchery. No one started marrying farm animals. Sadly, no one ever tracks down the naysayers to ask why their fear-mongering predictions failed to materialize. But then, fear-mongering is often the last bastion for those with no facts to back up their claims.

Consider the marriage arguments:

1. Its unnatural.
2. Its contrary to Gods will.
3. Its about illicit sex, not committed relationships.
4. The majority of Americans oppose such marriages.

Sound familiar? They should. They were the arguments posited in 1948 when Andrea Perez, a Mexican American woman, and Sylvester Davis, an African American man, challenged Californias interracial marriage ban in the state Supreme Court. The arguments reappeared when miscegenation went to the U.S. Supreme Court 19 years later in Loving v. Virginia .

In each case, the plaintiffs won, just as same-sex marriage eventually won.

This pattern repeats throughout American history: Cultural shifts emerge that expand individual freedoms, conservatives vigorously and even violently oppose such changes, but their opposition ultimately fails. Their intemperate arguments prove wrong, their melodramatic fears are unwarranted, and their panic-laden predictions are downright laughable.

The Virginia trial judge who upheld the 1958 conviction of Richard and Mildred Loving wrote that their interracial marriage, a violation of Virginia state law, was also a violation of Gods law.

Almighty God created the races, he wrote , and he placed them on separate continents ... The fact that he separated the races shows that he did not intend for the races to mix.

Talk about a facepalm moment.

The arc of American history has always gravitated toward liberalism . Not in the political sense, but in the broader moral code that has always stood for expanding individual rights, social equity and equality under the law.