There are multiple sides to every religion, every belief, every system. So many of these things react the way you expect them to on the base level. Even in death; people who "come back" report so many different things. When you die, your body dumps all of it's dimethyl triptamine into your bloodstream at once, making the last few seconds of your life last what feels like a massive amount of time, and making you see all sorts of things.
Voodoo has two main sides. The "white" side is primarily concerned with well-being, healing, protection, and good fortune. Their biggest job is to prevent the darker side from ever coming about; Red Voodoo. The darker side is usually performed only by a Bokor; think of them like a Voodoo mercenary. They do as a client asks, even if it's Red in nature.
As for witchcraft... Frankly, if someone gets hurt performing a ritual of some sort, they either were in over their head, arrogant, or simply untrained. Of course, there is accidental interference sometimes that can really mess stuff up, too. But witchcraft, like Voodoo, is primarily concerned with benefiting people.