If witches and witchcraft have become imbued with an identity that reaches far beyond their own existence, if they have become a symbol for something larger for Christians, then what are they a symbol of? It seems to me that witches served a symbolic role for the male, celibate religious authorities in Europe. Witches were not simply adherents to an alternative religiosity, and they certainly weren't turning whole towns into toads.
Indeed, most of those accused of witchcraft almost certainly weren't guilty of anything of the sort. Instead, their treatment at the hands of men, and the rationales used by those men, indicate that the oppression of witches was somehow symbolic of the oppression of women in general, of women's sexuality, and of sexuality in general. I hate to sound Freudian, but I really do think that in this case, the assertions by celibate men about the alleged sexual obsessions of witches are really a clear case of projection.
I think that it was the religious authorities who were obsessed and insatiable with their sexuality, but since their repressive ideology couldn't allow that, they had to project their desires onto others. If women, sexually evil beasts, were actually responsible for the priests' sexual desires, then the priests could in turn still feel holy -- and better yet, "holier than thou," more righteous and holy than the hated women around them.
When one group is systematically persecuted by others, and especially when the persecutors deliberately abandon normal standards of justice, procedures, and so forth, then it's important to look at whether the persecutors are just reacting to a perceived threat (real or imagined) or if they are instead reacting to something larger and using the victims as a scapegoat for larger fears. Sometimes both may be at work, too.