I think you are wrong. I don't think we should just sleep with whoever we want and just meet. This where the problem stems from. If Gilbert and co (and many people in our western world, i agree it is a commonly held idea) had a different moral perspective, the issue would never have begun.
I think it is the "job" of the person sleeping with someone to know their age. If you are going to sleep with someone, you better not be relying on a night club bouncer to make sure it is all above board. That is a gross lack of personal responsibility. Partly because if you are on the look out for sex, had a few drinks, it's late at night, and you are willing to sleep with people you don't know or care about, then you will find yourself in all sorts of potential trouble. This leads to practical problems - spurned lovers, under age sex, disease, unwanted pregnancy, often unfaithfulness to existing relationships. But over and above these concerns we have the moral framework that directs our behaviours. That is my opinion, and the one I am stating on an opinion based website.
Who am I to set the moral standards? Who are you, who is anyone, to set the moral standpoint? A relativistic argument will get nowhere fast on logic. This is where we will have to disagree. You see the issue here really is about where we take our moral and ethical standards from. If we are free to set our own - Chaos. If we just go by the law - well you can't legislate morality. So we need an objective standard. But most won't go for that b/c they want to say what they should be allowed to do or not.
Now as to whether my moral judgments are sought or not - this whole saga is deeply embedded in moral and ethical issues. It is why we are having the discussion, why it is news, why it titillates and stirs deep passions and beliefs. My moral position is just as valid as yours if you say everyone has the right to choose their moral position.
