I can well imagine there are people who moved to the red light district for cheap housing and a love of historic architecture who are genuinely surprised to find that there's so much sex, drugs and obnoxious tourist activity.

People tend to not really know what a neighborhood is really like until they've lived there for a bit. It's common for things to be different during the day versus nighttime or weekdays versus weekends and a lot of places change dramatically seasonally or have some very big annual event that impacts the entire area for days or weeks.