Pet Shop Boys fan

Modern version of a Friend of Dorothy.
A sophisticated euphemism for gay.

comes from assumption that only gays can enjoy music of British synth-pop duo Pet Shop Boys

There's someone you don't like and you want to insult them by calling them a "faggot," but you know that's awfully politically incorrect and will get you nailed as a bigot, so you say something like "I hear he's a Pet Shop Boys fan."