“I understand that my choice of supporting Proposition 8 has been the cause of many hurt feelings, maybe even betrayal,” Mr. Eckern said. “It was not my intent. I honestly had no idea that this would be the reaction.”

But the swift resignation was not met with cheers by those on either side.

Marc Shaiman, the Tony Award-winning composer (“Hairspray”), called Mr. Eckern last week and said that he would not let his work be performed in the theater. “I was uncomfortable with money made off my work being used to put discrimination in the Constitution,” Mr. Shaiman said. He added, however, that the entire episode left him “deeply troubled” because of the potential for backlash against gays who protested Mr. Eckern’s donation.

“It will not help our cause because we will be branded exactly as what we were trying to fight,” said Mr. Shaiman, who is gay. “But I do believe there comes a time when you cannot sit back and accept what I think is the most dangerous form of bigotry.”

Supporters of the marriage ban said that critics of Mr. Eckern were attacking freedom of expression, and they chastised the theater’s board for subjecting Mr. Eckern to a political litmus test.

“No matter your opinion on Prop. 8, we should all agree that it is wrong to intimidate or harass anyone for exercising their constitutional rights,” said a letter to the theater’s board president on Tuesday by Frank Schubert, campaign manager for Protect Marriage, the leading group behind the ballot measure.