If dark magic even existed I'd be dead by now,

it does exist somewhat...as long you repent and confess Jesus is you lord and savior then you won't have those curses and wouldn't even effect you.

Superstition is definitely a strange aspect of our species. I think it all boils down to our attempting to explain the unknown or yet to be explained workings of our natural world. Humans aren't exactly known for being rational, especially when we have such a strong tendency to convince ourselves that things are true even when there is absolutely no good reason to believe or even in the face of contrary evidence. Our lack of reasoning has caused the deaths of many more than just these "witches." It's also the reason why our National Infant Mortality rate here in the States is so high.