Having lived in Italy in the past and speaking the language, when I read posts like this I am not surprised when I hear that tourists avoid Naples. A few years ago, I was with a film crew working and I had numerous locals approach me and advise me to be very careful with the camera equipment because we were being watched and followed, not a comfortable feeling!
The local government needs to clean up this mess if they want a bigger piece of the tourism industry. That said, I go there about once every few years and I’ve never been robbed, pick pocketed or ripped off by taxi drivers but I’m sure some of these reports are likely true.