California Lieutenant Governor Gavin Newsom and San Francisco Mayor Ed Lee are among the 80 prominent leaders calling on San Francisco Archbishop Salvatore Cordileone to cancel participation in an upcoming march and rally against civil marriage for gay and lesbian couples.

Next Thursday's March for Marriage is being organized by the National Organization for Marriage (NOM) and the Family Research Council (FRC). Cordileone, a vocal opponent of marriage equality, is scheduled to speak at the event, which includes a march from the Capitol Building in Washington D.C. to the steps of the U.S. Supreme Court.

“We respect freedom of religion and understand that you oppose civil marriage for same-sex couples,” the leaders wrote in an open letter. “But the actions and rhetoric of NOM, and those of the event's speakers and co-sponsors, fundamentally contradict Christian belief in the fundamental human dignity of all people.”

“NOM has a long and well-documented history of publishing material that connects homosexuality with pedophilia and incest and falsely suggests that gays and lesbians are trying to 'inculcate children.' Likewise, the Family Research Council, which is co-sponsoring the event, has been designated a hate group by the Southern Poverty Law Center because of their vitriolic rhetoric; recently, a spokesperson for FRC blamed the growing acceptance of marriage for same sex couples for the Isla Vista mass shootings.”

“By standing alongside these individuals and organizations, you appear to be endorsing their troubling words and deeds, which directly contradict the U.S. Conference of Catholic Bishops' pastoral teaching that 'God does not love someone any less simply because he or she is homosexual. God's love is always and everywhere offered to those who are open to receiving it.'”

As of Wednesday night, a Faithful America petition calling on Cordileone to not “speak at hateful anti-gay rally” has accumulated more than 20,000 signatures.