my roomate in college got into black magic for a while, I'm not a fan, but I learned what I could, as I try and do with everything.
It seems that there is a large variety of magic that could be considered "black magic", though the stuff he was into was wiccan specific- magic that was for the purposes of controlling and/or destructing. There is great power int he destruction of soemthing- reducing an ordered thing to a state of increased chaos releases a great amount of energy which can be molded if one is trained. And this is not argued by science, this fits in well with physics. Take a stable object, and increase it's energy until is breaks apart, then harness the energy given off when that state of conbustion occurs- it no different than taking energy from the sun as it burns.
Wiccan belief states that everything you do comes back to you threefold, there fore any bad thing you do will result in bad things happening to you, three times over. Black magic seems to take somewhat different tact on this: it pretty much agrees, but doesn't really consider things to be bad or good- it's just manipulation. Results are results, and even the threefold return you expirience can be manipulated to your own ends, if worked properly.
As for the "point a stick at someone and they'll die", this could be no more than an extension of the idea "run with scissors and you'll put an eye out". it doesn't mean it will happen, but that it might. time and evolution of the phrase may have turned the idea of "I point a stick at you because I don't like you" into "I point this stick at you because I'm going to stab you with it" to "I point this stick at you, now you will die!"
alot of folk stories have very solid scientific or cultural facts behind them, but have been covered from time and verbal passing of the message.
many traditional medicine stories have this feature- a given story may talk about plant A not liking humans, and plant B liking them- this, when taken apart can prove to be a way to remember medicine. plant A is poisonous, and plant B is the antidote for the poison.
it's very commmon. Try taking the story apart logically first, before looking for magic. There may be magic involved, but most likely we're talking about very straight foreward issues.
