Not to discount genuine, supernatural evil:

I have always believed the provisions against witchcraft are because it is ultimately an attempt to subvert the natural order. Instead of women building homes and communities and ultimately a good culture, it diverts women to hanging out with other rejects that hate the system and want to see it twisted to their own ends. They aren't happy with their lot in our life, so they conspire to make others suffer.

I think a good modern analog for witchcraft would be feminism.