I think we have to adopt a realistic approach here.
No sane person thinks that a thirteen-year-old embarking on a sexual relationship is a good idea, but we have to deal with the world as it is, not as we would like it to be.
On that basis, I would be all in favour of the Pill being available, but with a proper health check, and hopefully some sound advice about protection from STD's, and how to approach a sexual relationship safely, without being coerced by bullying or peer pressure.
It is a shame that puberty and exuality occur ever younger, but that is a simple fact, we have no choice about that - only the effects it can have on children, and we would be failing them if we did not address these issues with a sense of calm maturity and realism instead of Mail-ish hysteria and finger-wagging which helps no-one.