We all have moral preferences and beliefs about how the world is and should be. Having these views challenged can be painful, so we tend to avoid people with differing values and to associate with those who share our values. This self-segregation has become much more potent in recent decades. We are more mobile and can sort ourselves into different communities; we wait longer to find and choose just the right mate; and we spend much of our time in a digital world personalized to fit our views.
Source: Why I Was Fired by Google – WSJ