A variant of "whatever floats your boat" or "to each his own," said upon learning another individual's tastes or preferences, implying mild surprise nested within an unwavering ambivalence.
Marissa: "I really love Buffy: the Vampire Slayer"
Eric: "Whatever fucks your wife...."
Mike: "She said that she'd date that creep if he wasn't her roommate."
Tony: "Eh, whatever fucks your wife, man."