Authoritarian societies tend to work with whatever "
official version" of reality is preferred- thus unless information is carefully controlled, cognitive dissonance becomes a way of life.
The concept of blackwhite is a response to a society in which contradiction is the primary mode of operation. It is a means of avoiding cognitive dissonance by submitting to authority- whatever the authority says is correct and always has been, simply because the implications of thinking otherwise are difficult to deal with from an individual perspective.