Well, sure, breaking young girls’ hearts isn’t a nice thing to do – but then, neither is breaking anyone else’s heart. Singling out young girls makes Jackson sound like, well, someone who particularly targets young girls for their lustful purposes. (Which leads to the obvious question: how young is young?)
Actually, from a point of view of self-preservation, young girls’ hearts are probably the safest ones to break. Older, more cynical girls are more vengeful, as are boys of any age (the latter are also often violent – and Jackson is on record as “a lover, not a fighter.”) But I suppose when you can afford personal security like Jackson had, safety is less of an issue.