Well there should NOT be a arbitrary age for when you can have or not have sex legally. Every person is different, has different needs and desires, that cannot be meet by some hard line law.

And for the need to protect the children, how bout protecting the children who are having consensual sex from those that want to prosecute them for it. When its to kids having sex, say a 12 year old girl and a 13-14 year old boy, the boy is prosecuted for a sex crime. And now that he's the "offender", many are prosecuted as adults. So long adult sentences, and a life time on the sex offender list, all done in the name and by the law to protect children.