Growing up in Flatbush and going to High School 1967-1971 seemed to me that Brooklyn, at least, (I don't know about the other Boroughs) was very unsafe in the 1970's. Of course in those days many areas were safer than others.
Today some of the most unsafe neighborhoods from back then are so hot someone making good money can't afford to rent or buy there. Surprises me a lot, but very true. Brooklyn, almost all over, is a very hot ticket.
Now, I visited the Rockaways and my sister was a nurse at Far Rockaway Hospital mid 60's to mid 70's so that is a part of Queens I knew. Far Rockaway was, and is, unsafe. It may be slightly better now, as the Rockaways has spread somewhat into neighboring Far Rockaway, similar to what happened to Williamsburg and Bushwick.
I don't blame Sanders' mom (if true).
Any chance that cameras, cell phones and videos, make it seem less safe. CBS, NBC, ABC, local news always lead with video of some mugging, shooting or other violent crime THAT THEY HAVE VIDEO OF. If they don't have video you might not even get a mention. In the 1970's there was no video.