The philosopher F. W. Nietzsche said: "Insanity in individual is something rare--but in groups, parties, nations, and epochs, it is the rule." What behaviors committed by groups might be considered psychotic if an individual were to perform them?
Here's a list of possible actions/behaviors that apply to the quote above (that you can expand on).
1) Following the ideals of Hitler. The Nazi Germany is the perfect example of a nation following the ideals of an insane individual. Mass killings, if performed by individual, is considered a psychotic behavior. But ...
Examples of behaviors committed by groups that might be deemed as psychotic are noted.