One is prostitution, a form of sex work which is illegal in most of the United States. The American public have varying feelings about its legal status, how enforcement should be carried out, etc. Public opinion doesn't support measures which endanger sex workers (which FOSTA does), because they're already an at-risk group.
A separate issue is human trafficking, which is moving people across borders for the purpose of slavery/forced labor, including sex slavery. Public opinion is rightly massively against slavery in any form.
What I would like to know is, how much slavery was taking place through the Craigslist personals section? How much of it goes on in America? Can we get some real data injected into this discussion about the nature and the extent of actual forced sex labor? Scorched earth tactics might be appropriate if America has developed a serious slavery problem (again), but they need to be justified with facts.
I've run across people who want to take a scorched earth approach to eradicating prostitution (which will not work any more than the war on drugs did). They refer to all prostitution as trafficking in order to conflate the two issues, mislead the public and build support for their radical policies. There is also a class of people who have used FOSTA as an opportunity to expand government power. Neither of these agendas reflect public opinion.