How can the witches in Macbeth be seen as manipulative?

On one level, the witches in Macbeth can be seen as responsible for all the grisly events in the play. They tell Macbeth he will be both Thane of Cawdor and King of Scotland. When their first prediction comes true almost immediately, Macbeth then believes he is destined to gain power by killing Duncan. Furthermore, they lull Macbeth into a false sense of security by telling him that no one born of woman can defeat him. As such, it's possible to argue the witches manipulate Macbeth by telling him partial truths, but not the whole truth, and so they falsely present the future in a way that causes Macbeth to pursue a murderous rampage.

It's important to interrogate this idea somewhat, though. While it's absolutely possible the witches are manipulative, it's also possible they are more neutral than they first appear. After all, their prophecies are rather vague, and it's Macbeth who interprets them as excuses to murder. As such, though it's certainly possible that the witches manipulate Macbeth, it's also possible that Macbeth's own ambitions and interpretations of the prophecies are to blame.