Despite attempts by a conservative American mothers' group to have it pulled from sale, the new Archie comic, which features a gay marriage, has just sold out.

Tracing the adventures of the teenagers Archie, Betty and Veronica in the small town of Riverdale, the Archie storyline has been running for 70 years and is one of America's most popular comic series. Its publisher described the marriage of Kevin Keller, the series' first gay character, in the latest issue as "a historic moment", announcing yesterday that the Life with Archie #16 had sold out.

The strong sales follow a call from the American Family Association's website One Million Moms for Toys R Us to stop selling the new Archie issue. The conservative Christian group is concerned that "children are now being exposed to same-sex marriage in a toy store". "Please remove all the same-sex 'Just Married – Archie' comic books immediately from your shelves. My decision to shop in your stores depends on it," they have written to the retailer.

Homosexuality is a topic which is "too complicated" for children to understand, say the mothers, and "a trip to the toy store turns into a premature discussion on sexual orientation and is completely uncalled for".

But Archie Comics co-chief executive John Goldwater has said that the company "stands by" the new issue. "Riverdale is a safe, welcoming place that does not judge anyone. It's an idealised version of America that will hopefully become reality someday," he said.

"We're sorry the American Family Association/OneMillionMoms.com feels so negatively about our product, but they have every right to their opinion, just like we have the right to stand by ours. Kevin Keller will forever be a part of Riverdale, and he will live a happy, long life free of prejudice, hate and narrow-minded people."

Announcing yesterday that the Kevin Keller issue had sold out, Goldwater said that Archie's fans "have come out full force to support" the gay character. "He is, without a doubt, the most important new character in Archie history. He's here to stay," Goldwater added.