A plot device in a story which entails the villain giving a convincing lecture to its interrogator, usually in an attempt to justify itself; often successfully convincing the hero of his or her own moral shortcomings.
"You'd like to quantify me, Officer Starling. You're so ambitious, aren't you? Do you know what you look like to me, with your good bag and your cheap shoes? You look like a rube. You're a well-scrubbed, hustling rube with a little taste. Your eyes are like cheap birthstones - all surface shine when you stalk some little answer. And you're bright behind them, aren't you? Desperate not to be like your mother. Good nutrition has given you some length of bone, but you're not more than one generation out of the mines Officer Starling. Is it the West Virginia Starlings or the Okie Starlings, Officer? It was a toss-up between college and the opportunities in the Women's Army Corps, wasn't it? Let me tell you something specific about yourself, Student Starling. Back in your room, you have a string of gold add-a-beads and you feel an ugly little thump when you look at how tacky they are now, isn't that so? All those tedious thank-yous, permitting all that sincere fumbling, getting all sticky once for every bead. Tedious. Tedious. Bo-o-o-o-r-i-ing. Being smart spoils a lot of things, doesn't it? And taste isn't kind. When you think about this conversation, you'll remember the dumb animal hurt in his face when you got rid of him. If the add-a-beads got tacky, what else will as you go along? You wonder don't you, at night?"
—The Hannibal Lecture by Hannibal Lecter, The Silence Of The Lambs (book)