I can't figure it out, half the time he's wooing women on the piano and smacking them on the behind as they walk away together and the other half he's dancing in leather at gay clubs.
See, I'm telling you, Stewie, if not gay, must clearly by metrosexual. Just like Jean Francois.
Don't forget he also had his way with a Mrs. Piggy in front of Kermit (granted that was to extract information.) Actually, I heard they are making a movie and a substantial part was to be devoted to Stewie's sexual ambiguity.