A "stepford fag" is a gay man who wishes to get married, have kids, and live in a more traditional ‘heterosexual’ community.
Some people use the term to refer to gay men they believe are living an imitation heterosexual lifestyle.
First man: "You know Brain Kinney?"
Second man: "Yeah- that wild guy who used to party all night, haven’t seen him around for a while."
First Man: “Not surprising. Heard he’s settled down and got married.”
Second Man: “Never thought he was a stepford fag.”