But, the thing is, those things mostly happen because prostitution is illegal.
Just think of history.
When pharmacists could legally sell cocaine and heroin, criminals had no interst in it and nobody was getting shot over it and quality control measures were in place. Once it was illegal all sorts of bad stuff happened leading to addiction, crime, violence and crappy drugs.
Same thing happened with booze in the 20s.
Now take a look at gambling in America. People used to get shot all the time and casinos used to be rigged all the time back when it was illegal. Now that it's legal and there are casinos everywhere that doesn't happen anymore. Nothing is rigged becasue there are controls in place and peolpe don't generally seek out illegal places where they might get killed over a debt, because it's easier and safer to go to the legal places.
Think about what would happen if prostitution were legalized. Very, very quickly corporations would start opening up McCock's and McPussy's franchises. They would be safe, the workers would be there voluntarily and people would choose them over finding someone on Backpages.com - where women would be more likely to be underaged and trafficked.
The financial incentive to bring forced labor into the industry would dry up pretty quickly. And once the financial incentives are gone, criminals would run away from it - because they could never compete against Sam Walton's Pussy-Mart.
Sure some creeps would still try to serve the pedo market, but their numbers would be greatly reduced because the risk/reward ratio would be different. Same as how we still have some moonshine, but the amount of people going blind from bathtub gin is much, much lower than it was in the 20s.