[ Giles does, in fact, pick up a knife -- their best one, at that. He whirls to face her, backing up slowly with the blade held between them and an open doorway at his back. He's clearly on the defensive, not intending to make a move unless she does.

With a very deliberate, forced calm: ]

I will not stand by. But you do not want to kill me any more than I wish to fight you-- I will be back the next day, unharmed, and I will return the favor.