In his book Fearless, Max Lucado writes about the power fear possesses to turn us into beastly people:

[Fear] turns us into control freaks … [for] … fear, at its center, is a perceived loss of control. When life spins wildly, we grab for a component of life we can manage: our diet, the tidiness of our home, the armrest of a plane, or, in many cases, people. The more insecure we feel, the meaner we become. We growl and bare our fangs. Why? Because we are bad? In part. But also because we feel cornered.

Martin Niemöller documents an extreme example of this. He was a German pastor who took a heroic stand against Adolf Hitler. When he first met the dictator in 1933, Niemöller stood at the back of the room and listened. Later, when his wife asked him what he'd learned, he said, "I discovered that Herr Hitler is a terribly frightened man." Fear releases the tyrant within.