When people are afraid, they tend to see their problems in black-and-white terms. They tend to block out contrasting information, and want a muscular solution. These are the characteristics that lead to authoritarianism, which we are all prone to sometimes.
I often hear laments about the polarization and partisanship that comes from people - other people - being closed-minded, narrow-minded, or, again, seeing things only in black and white.
As I review the psychological studies I know and the anecdotes I can think of, I have a hunch: we only see the world in black-and-white terms when we are fearful. When we are reasoning calmly, everyone is able to see positions in the middle.