LOS ANGELES — At last count, 667 people, give or take, have screen credits on “Ender’s Game.”

One of them turned into a problem this week.

A planned boycott aimed at this science-fiction film, which is to be released on Nov. 1, gained momentum just as Summit Entertainment and its partners were getting ready to introduce “Ender’s Game,” with two of its stars, Harrison Ford and Asa Butterfield, at the Comic-Con International fan convention in San Diego next Thursday. At issue is the author of the novel on which the film is based, Orson Scott Card; his views on homosexuality; and his public stance against same-sex marriage.

A book with a futuristic battle story published in 1985, “Ender’s Game” has nothing to do with gay marriage. Indeed, Glaad, a gay-rights organization that tracks media, reviewed the script and found nothing to criticize.

As for Mr. Card’s background and views, they were hardly a secret. A Mormon and a descendant of Brigham Young, he was on the board of the National Organization for Marriage, which has opposed same-sex unions, from 2009 until this year. In March a DC Comics project with Mr. Card as a co-writer fell apart when its illustrator, Chris Sprouse, quit as an online petition called for Mr. Card’s removal.