I don't have any quotes from the author herself, but may be able to offer an explanation as to why something with such obviously dire implications was included in a children's book.
Magical potions have been known of and coveted by us muggles for hundreds of years, featured even in Shakespeare's plays.
During the 19th century it was commonplace to see alchemists and wandering charlatans peddling 'potions', a staple among them being love potions so that customers could attempt to win (read: force) the affections of those for whom they yearn.
I can't really find any sources on specific occurrences or recipes of love potions in the real world, other than this painting that proves it was at least a known concept as far back as 1903.
As J.K. Rowling liked to incorporate the existence of the wizarding world into our own, such as including the witch burnings from the 16th century into HP canon, it would have been quite unusual to not include something so crucial to the myth of magic into the HP universe.
Therefore, rather than not addressing the possibility of such a thing existing, it is likely she attempted to incorporate the potion into the story and attempt to use it in a more light-hearted way, by insinuating it was used for school-kid crushes as opposed to date-rape.
Note: this is in a universe where sex was never even discussed in a boarding school that included children of both genders who, for the latter years, were of legal age to have sex. If we thought harder about the 'adult' implications of the HP universe, my first question would be how by Merlin's beard could Hagrid possibly exist, and why he ever bothered to ask Madame Maxine which of her parents was a giant.
In addition, the Imperius curse existed, which could be used for equally if not much more diabolical sexual crimes, so including the possibility of the 'love-potion' would never have added any extra layers of depravity to the equation.
As for why it was included in the school curriculum and made available as an everyday purchase in children's shops, Professor Snape says to the students that he is going to teach them to make poisons that will potentially kill their enemies, so clearly it is assumed that they will act morally responsibly in their dealings with potions.