And US companies should choose to not, and perhaps should be banned from, operating in countries where their services are used for human trafficing. FB and Google shareholders should demand this from their companies. Of course it will mean some reduced revenue, but I think most Americans regardless of political affiliation would agree that human trafficing is just unacceptable.
Additionally, Facebook and Google are very smart. They can connect dots (accounts). They know who is selling humans, and they could perma-ban these people. Essentially it should be possible to prevent these people from ever using any account on any of the major tech services.