Bad Scene, Good Movie
The Onion's list of 15 worst scenes in good movies and best in bad.
I disagree with their first choice. The explanation scene is Psycho is more painful to watch than anything else in the movie but it's intentional. Instead of dimissing the madness, it dismisses the explanation, any explanation for such actions. (Also it satirizes the "this-is-why-the-bad-guy-did-it" dialogue found in every thriller from D.W. Griffith to Silence of the Lambs.