The following video was made by a woman who had been suffering in an abusive relationship for many years. In personal terms, she explains the underlying psychological principle of cognitive dissonance, and how it kept her from realizing what was really going on and taking the necessary steps to end it.
We commt to a belef on the basis of emotion, and then we use our intellect to defend it -- which is why political and religious arguments usually lead nowhere. When you have an idea that you are deeply committed to and you encounter a fact which contradicts it, as in the case of the group described in the video below, cognitive dissonance is the result. You put your intellect to work not to seek the truth, but to reduce the dissonance if the truth is just too uncomfortable to face because it is tied up with your sense of self.
Political, racial, religious, and other forms of cognitive dissonance have ruined many Thanksgiving and Christmas dinners, outdoor barbecues, and couples get-togethers; and at the opposite extreme, it can provide the basis for rioting and war.