Prejudice toward those with differences is a result of fear, denial, and ignorance:

We fear our own possible fate: the thought of being blind, deaf, paralyzed, senile, chronically ill, or “losing our mind” can be terrifying. And we also dread the way we might be treated if we experienced any of these conditions: the social alienation, disapproval, exclusion and rejection we might face from our community, peers, families and friends. We are horrified by the thought of being repulsive to others, because we recognize our own sense of revulsion and knee-jerk reactions to the “funny-looking” and the “abnormal.” 

We avoid identifying with those on the margins of society. We mentally push these ‘others’ as far away from us as possible by categorizing and stigmatizing, dehumanizing and devaluing them. Our society has become so alienated and dehumanized that we hide away our elderly, incarcerate mentally ill children, and deny pain relief to poor, uninsured women during labor.

People tend to offer greater leeway for the behavior of those we identify with and empathize with as “our own kind’. 

And we tend to discount the suffering, sentient experience and worth of those we consider the “other.”