A duck's quack does not echo, and no one knows why?
A black hole isn't actually a hole at all. It is a pinpoint and extremely dense piece of matter that has an enormous amount of gravitational pull because of it.
That fact that it isn't actually a hole isn't up for debate. The infinite energy density is though.Gotta be a "fact". Nobody knows what's at the center of a black hole...but if it's an actual thing made of matter then the point at the center would exhibit infinite energy density.
If you pinch your nose closed, you can't hum.