When the villain tries to justify his worst actions as necessary means to some noble purpose to someone who is fully conscious of what he really does, and that someone answers him by telling him that he's not accomplishing anything greater than murder, destruction and cruelty. This someone calling the villain out could be in a position of demonstrable superiority, or one of abject impotence.
Needs a Better Title
, I think. This is currently lumped with Shut Up, Hannibal!
, which should properly be the more aggressive and less philosophical version of this.