1) Am I the only one who looked at the girl’s face first?
2) While the photograph in question obviously uses sexuality, I’m not sure I’d want to say that it is primarily a sexual picture. The sex is implicit, not explicit; the girl’s pose might give rise to sexual thoughts, but it is not an invitation. She’s just a person sitting in a way that an onlooker might find sexually attractive.
3) If the girl doesn’t look 15 in the photo, how is this bait for pedophiles? The distinguishing characteristic of pedophilia is attraction to women who are—and who look—prepubescent. If you take a girl who looks 24 and tell a pedophile she’s actually 9, that’s not going to do it for him.
4) I agree with @wundayatta: we live in a tawdry culture that likes to pretend it is Puritan. This is a scandal because it can be, not because the majority wants us to go back to the days of burying our sexuality and pretending that no one else thinks about sex. The scandal itself is just a further titillation. Something to talk about in the afterglow of the main event.
5) To answer @rebbel‘s actual questions, then, I do not think that a woman sitting with her legs apart is disturbing. We sometimes like to say it is, but it’s really just something to talk about. There’s nothing wrong with it. Women should sit however they please, and those who do not like it can look away. Those who find the position to be always sexually loaded, and who find that to be offensive, are probably those who experience the most incontinence regarding their sexual thoughts.
Just as many of those who insist that being gay is a choice turn out to be gay themselves (and who said it was a choice because all they were aware of was their struggle against their own sexuality), many who find sex to be all around us are those who cannot prevent themselves from sexualizing everything in sight. What we really see in these pseudo-scandals is a society’s repressed sexual thoughts. These are projected onto a target—in this case a 15-year-old girl—so that we can have permission to look at all of our own curiosities, anxieties, and frustrations.
And lest this sound like too academic of an opinion, I might add that it’s rather similar to an episode of South Park.