Yeah, Stewie could swing either way.

I can see the dialogue exchange now:
Stewie sitting on a playground swing. Brian walks over.
Stewie: "Oh, hey dog -- what'cha doin'? Workin' on that novel?"
Brian: "Bite me. What are you doing that's so important?"
Stewie: "Just a swingin' on the ol' kiddy swing, Bri'."
Brian: "So ... so you love swinging?"
Stewie: "Oh god, yes."
Brian: "Ever try other swings?"
Stewie: "You know, I find I like a littloe of both. But the pole is my favorite."
Brian: "Ah huh. So, you're a swinger?"
Stewie: "Yeah. Why do you ask?"
Brian: "No reason."