I'm not sure that the parent poster was being serious, but I imagine the view is that if you give such a thing to a teen, that they may feel it reduces the risks associated with sex enough that they will be willing to have loads of unprotected sex. I could argue that this is true to some extent[1], but probably no more so than with current contraceptives.

[1] Apparently things like oral sex and anal sex are infinitely more popular nowadays because they are seen as ways to have sex without getting pregnant (even though it doesn't reduce the STD risk).

I wish more countries had protection for reproductive rights like South African's Bill of Rights: http://www.gov.za/documents/constitution/1996/96cons2.htm#12