The Church of Jesus Christ of Latter-day Saints encouraged its members to work to pass Proposition 8 by volunteering their time and money for the campaign. California voters approved the measure Tuesday.
The Friday evening protest comes a day after people demonstrated outside a Mormon temple in Los Angeles. About 1,000 gay-marriage supporters waved signs and brought afternoon traffic to a halt.
On Thursday, outside the gates of a Mormon temple his father helped build, Kai Cross joined more than 2,000 gay-rights advocates in a chorus of criticism of the church's role in the likely passage of a statewide ban on same-sex marriage.
Once a devout Mormon who graduated from Brigham Young University, the 41-year-old Cross was disowned by his family and his church after he was outed as a gay man in 2001.
"They are on the losing side of history," Cross said Thursday of the church's opposition to gay marriage. Cross and other protesters blame leaders of the Church of Jesus Christ of Latter-day Saints for encouraging Mormons to funnel millions of dollars into television ads and mailings in favor of Proposition 8.
The ballot measure was sponsored by a coalition of religious and social conservative groups, would amend the California Constitution to define marriage as a heterosexual act. It would override a state Supreme Court ruling that briefly gave same-sex couples the right to wed.
According to the CBS News Election and Survey unit's analysis, black voters overwhelmingly voted in favor of Prop. 8 - by a 70 percent to 30 percent margin. Hispanic voters overall favored the measure as well but only by a 53 percent to 47 percent margin. White voters were slightly on the side of approving it, 51 percent to 49 percent.
There is disappointment that the African-American community, which just saw the election of the first black president, voted overwhelmingly against same-sex marriage, reports CBS Early Show correspondent Hattie Kauffman.
The protest came amid questions about whether attempts to overturn the prohibition can succeed and whether the 18,000 same-sex marriages performed in California over the past four months are in any danger.
For Cody Krebs, 27, four months was not enough time to fulfill his "intense hope" to marry one day; he and his boyfriend have been together for little more than a year, so they aren't ready to wed.
On Thursday, Krebs dodged eggs hurled at protesters from an apartment building. He said he'd seen worse growing up in Salt Lake City.
"It's important to come out like this because it gets the gay community into the public eye," Krebs said. "I feel like this has started a lot of conversations that had to get started."
The demonstration began outside the temple in the and noisily spilled through the western side of the city, with chants of "Separate church and state" and "What do we want? Equal rights." Some protesters waved signs saying "No on H8" or "I didn't vote against your marriage," and many equated the issue with the civil rights struggle.
Two people were arrested after a confrontation between the crowd and an occupant of a pickup truck that had a banner supporting Proposition 8. One demonstrator ended up with a bloody nose in the fracas. Seven arrests occurred during Los Angeles-area street marches late Wednesday.
The temple protest was organized by the L.A. Gay & Lesbian Center. Its chief executive, Lorri Jean, announced a Web-based effort dubbed InvalidateProp8.org to raise money to fight the constitutional amendment.
Gay-marriage proponents filed three court challenges Wednesday against the ban. The lawsuits raise a rare legal argument: that the ballot measure was actually a dramatic revision of the California Constitution rather than a simple amendment. A constitutional revision must first pass the Legislature before going to the voters.
Andrew Pugno, attorney for the groups that sponsored the amendment, called the lawsuits "frivolous and regrettable."
"It is time that the opponents of traditional marriage respect the voters' decision," he said.
The high court has not said when it will act. State officials said the ban on gay marriage took effect the morning after the election.
"We don't consider it a `Hail Mary' at all," said Kate Kendell, executive director of the National Center for Lesbian Rights. "You simply can't so something like this - take away a fundamental right at the ballot."
With many gay newlyweds worried about what the amendment does to their vows, California Attorney General Jerry Brown said he believes those marriages are still valid. But he is also preparing to defend that position in court.
The amendment does not explicitly say whether it applies to those already married. Legal experts said unless there is explicit language, laws are not normally applied retroactively.
"Otherwise a Pandora's Box of chaos is opened," said Stanford University law school professor Jane Schacter. Still, Schacter cautioned that the question of retroactivity "is not a slam dunk."
An employer, for instance, could deny medical benefits to an employee's same-sex spouse. The worker could then sue the employer, giving rise to a case that could determine the validity of the 18,000 marriages.
Supporters of the ban said they will not seek to invalidate the marriages already performed and will leave any legal challenges to others.
A 2003 California law already gives gays registered as domestic partners nearly all the state rights and responsibilities of married couples when it comes to such things as taxes, estate planning and medical decisions. That law is still in effect.