I think we need a sticky just on this. There is a lot of misunderstanding.
One thing I just learned and verified is that my body is actually the single biggest source of that noise in my passive basses, which is why most of it goes away when I'm connected via a conducting path to the output ground. Also, I discovered long ago that one very unglamorous but effective way to do that is attach a bare wire taped to the metal case of the instrument cable plug in the bass output jack and attach the other end of the bare wire around your wrist to maintain a conducting path.
Otto