Following a shareholders' meeting of the Seattle-based coffee giant on Wednesday, the Washington, D.C.-based National Organization for Marriage announced a "Dump Starbucks" protest.
The group says it will place ads throughout the country, as well as in the Middle East and Southeast Asia, urging consumers to boycott the company. The group is supporting a referendum effort to overturn a recently passed law legalizing same-sex marriage in Washington state.
"We will not tolerate an international company attempting to force its misguided values on citizens," said the group's president, Brian Brown, in a written statement announcing the boycott.
Phone and email messages left with Starbucks seeking comment on the threatened boycott were not immediately returned on Wednesday.
CEO Howard Schultz defended the company's stance on gay marriage during the shareholders' meeting, saying it was made "in our view, through the lens of humanity, and being the kind of company that embraces diversity."
Schultz received loud applause when he told the group that the decision to support gay marriage was "not something that was a difficult decision for us."
Starbucks is just one of several prominent Pacific Northwest businesses that have expressed their support for same-sex marriage, including Microsoft Corp. and Nike Inc.
Schultz was asked by three shareholders about the company's stance, with one asking: "Is it prudent to risk the economic interests of all the shareholders for something that might affect the private lives of a very small percentage of our employees?"
Schultz responded that he believed the success of the company, "which is linked to shareholder value, has a great deal to do with whether or not our people are proud of the company they work for and feel they are part of something larger than themselves."
"I would say, candidly, since we've made that decision, there's not been dilution whatsoever in our business," he said.
Maggie Gallagher, co-founder of NOM, said the main focus of the group's protest is to make sure Starbucks knows that not all of their customers agree with their philosophy on gay marriage. Gallagher said that in addition to ads, the plan is to have customers call Starbucks managers around the state to let them know how they feel.
"We would be satisfied if, in the future, they would refrain from entering in these hot-button moral issues," she said.
Human Rights Campaign, a national gay-rights group, said Wednesday it would soon launch a campaign asking consumers to support Starbucks.
That group's president, Joe Solmonese, called NOM's protest "typical bullying tactics."
Washington state's gay marriage law takes effect June 7, but could be put on hold by a referendum effort supported by the National Organization for Marriage, which was involved in ballot measures that overturned same-sex marriage in California and Maine.
A group called Preserve Marriage Washington filed Referendum 74 immediately after Gov. Chris Gregoire signed the new measure into law last month.
If they collect the more than 120,577 valid voter signatures needed by June 6, the law will be put on hold pending the outcome of a November vote. Separately, an initiative was filed at the beginning of the legislative session that opponents of gay marriage say could also lead to the new law being overturned.
Gay marriage is legal in New York, Connecticut, Iowa, Massachusetts, New Hampshire, Vermont and Washington, D.C. On Wednesday, New Hampshire lawmakers rejected a bill that would have made their state legislature the first one to repeal a gay marriage law. Maryland legalized gay marriage this year as well, though opponents there are promising to challenge it with a ballot measure.