I agree with your first paragraph, but I've heard from experts in the field that human trafficking is already illegal, criminalising sex work just scares the victim into silence.

A lot of sex slaves here in Australia are immigrants who agreed to an illegal and unethical deal in order to flee their home countries. So when the cops bust a trafficking ring, what do they do? Send the girls back home to the regime they fled. That's not helping. The government should give them a visa and let them work here if they want.