I think it is very unfair and inflammatory to suggest that RS is somehow promoting "human trafficking" because he discusses various red light districts. It also lacks a certain understanding and definitely any nuance of the subject. You are a great poster here Ms. Jo and I'm actually disappointed in your statement (although the overall subject is good to discuss and I respect your passion).
First and foremost, there is a HUGE difference between "human trafficking" and the sex trade and red light districts. A red light district includes various sex industry businesses, not all of which involve prostitution. Many people visit the districts with no intent to partake of prostitutes or even to gawk.
Next, these places have made an attempt to address some very serious issues involving the sex trade and prostitution. Human trafficking is a serious problem and while I doubt this approach solves those problems, doing nothing or taking the US approach of arresting the prostitutes also does not solve the problem. One serious issue is health care and dangerous conditions. Their approach does seem to have some positive effects on these issues (although again I doubt they come close to solving them).
My take on how RS deal with this in his books is that he knows people will find these areas or seek them out (for whatever their reasons). Better to explain a little something. I haven't read all of his descriptions mentioned, but the Amsterdam description is very clear that there are serious problems, including "immigrant exploitation," "shameless commercialization," and that many people will be offended (in addition to safety concerns). One can debate if he says enough or uses just the right words, but he doesn't sugar coat it by any means.
Seediness has long been a tourist draw. Jack the Ripper tours exploit what were gruesome murders. Chicago tours stop at notorious gangster murder scenes. Freeway traffic jams are sometimes caused by rubber-neckers that want to see the accident as the pass by. It's human nature.
Finally, I think there is a lot to be said for having people be aware of these places. When I first visited Amsterdam, I definitely wanted to see it (not to partake but I was a curious young man). I found some of it titillating to be sure, but I also was profoundly moved at seeing women offering their bodies in that way and it really disgusted and saddened me. It's not something many Americans ever see in the US.