A petition thanking Starbucks for supporting gay marriage got a boost from the progressive group MoveOn.org this week.

The National Organization for Marriage (NOM), the nation's most vociferous opponent of gay marriage, launched its “Dump Starbucks” boycott after Starbucks CEO Howard Schultz defended the company's decision to back Washington state's recently-approved gay marriage law.

The group SumOfUs.org responded with an online petition thanking Starbucks for its support.

Now the progressive group MoveOn.org is calling on its members to join the campaign. Earlier this week, the group posted the petition on its own website.

“We don't want to just criticize corporations when they do bad,” the group wrote. “We want to encourage them when they do good.”

Starbucks has said the boycott was having no impact on its business.

“We're not seeing any impact,” Starbucks spokesman Zack Hutson told Seattle alternative The Stranger.

As of Sunday morning, supporters were outpacing opponents 18 to 1, with more than 463,000 people signing a thank you card and just over 25,200 pledging to avoid Starbucks shops and its retail products.

NOM is also fighting off criticism that it pursued a strategy to pit minority groups against gay marriage supporters.