Sometimes we love our bad guys. It is a joy, to hate a character in fiction. Such a character can literally be perfectly awful, because that character is a created thing. The author intended the foil to act so, within the context of the story. We can both revile and enjoy them. We are safe within the fiction, despite the distress it sometimes causes; we know that no real harm has come to anyone.
The reactions fiction provokes, though, are real to us in a profound, internal, way. The hate of the adversary is real, despite the fiction.