Are parts of Naples unsafe for walk?

On the TV we often hear that some parts of Naples are unsafe for walk and it is very hard to understand it, I mean Naples is in Italy, not some middle east country!? Is it really true and what parts are unsafe and for who, only strangers and tourists or for Italians too?

Me and my boyfriend went to Naples almost 3 years ago and since we were interested in seeing an exhibition in Capodimonte, we booked a hotel that is positioned so that we can reach it without difficulties. The hotel was on the limit with Secondigliano, a very unsafe part of Naples (I think it is very known for its criminality), and when we arrived the landlady asked us why we want to go for a walk since there is nothing to see. She insisted that we don’t go out from the hotel at 10 in the evening and it seemed very strange to us. When we arrived home, some friends asked us were we crazy to stay in that part of Naples, but fortunately nothing bad happened to us. I repeat, I heard that there are some parts of Naples unsafe for walk, like Secondigliano and Scampia (the centre of Camorra), but to us nothing bad happened. Sometimes it can be unsafe also for Italians to go there.