Jews and heretics were often treated as scapegoats for other social problems and witches ended up no different. Regions with the most social and political unrest also happened to be those with the greatest problem with witches. Every social, political, and natural problem was blamed on witches. Crop failure? Witches did it. Well gone bad? Witches poisoned it. Political unrest and rebellion? Witches are behind it. Strife in the community? Witches are influencing people.
Lest anyone imagine that the persecution of witches has been relegated to the distant past, it must be noted that witch hunts -- and killings -- continue well into our own "enlightened" times. The church's creation of witchcraft and devil worship has exacted a heavy and bloody toll on humanity which still has not yet been fully paid.
In 1928, a Hungarian family was acquitted of killing an old woman they thought was a witch. In 1976, a poor German woman was suspected of being a witch and keeping familiars, so people in the small town ostracized her, pelted her with stones, and killed her animals. In 1977 in France, a man was killed for suspected sorcery. In 1981, a mob stoned a woman to death in Mexico because they believed that her witchcraft incited an attack on the Pope.
In Africa today, fears of witchcraft cause the persecution and death of people on a regular basis. Parents who fear that their children are possessed or are witches either kill them or turn them out into the streets. Government authorities have tried to put a stop to such nonsense, but they haven't had much luck. Both traditional African religion and Christianity contain enough to feed people's superstitious fears and this leads to others being harmed.
It's not just allegations of witchcraft which causes people to behave like this. Many other things can become the object of hysterical persecutions and prosecutions. Sometimes the alleged threats are genuine and sometimes they are not; in either case, the threats are magnified to such a degree that people no longer feel bound by traditional standards of justice or morality in order to confront their enemies. The consequences are almost always violence and suffering pursued in the name of good and God.