Okay, so to modern people who have seen thousands of TV shows, movies, and internet videos, and read who knows how many books. We understand the world is fully of wondrous and strange things. To us, this video is funny. Imagine what you would think if you were an illiterate medieval peasant and saw foxes doing this with no frame of reference. I'd probably never sleep again.
No need for a witch hunt. Preindustrial societies had unfortunately high mortality for infants and children. Obviously the free-floating spirits of dead children are latching on to foxes so they can communicate with the material plane. Nothing to be worried about...