One way to look at this is as a wedge issue to get the feds' foot in the door to start to regulate the originally neutral Internet as a first step on supposed beneficial purposes, and then seek gradually broader application and more control.
Why have a new law to do this? As they called it "sextortion" what's wrong with just extortion simple? We have blackmail laws, too, and laws against intentional infliction of emotional distress. Why do we need the feds in on this, when it fits well with states' police powers?
We must always look beyond the supposedly beneficent purposes to passing new laws when there's a suspiciously political motive involved.