As we evolved and other parts of our rational minds developed, this fearful part of our brains remained. It is like the appendix that we no longer need.
We feared what was different. We didn’t trust the tribe of cannibals that did not look like us. They wore red feathers, we wore blue. We hated and feared them. They hated and feared us. They attacked us. We feared them more. We attacked them. They feared and hated us.
So anyone who doesn’t look like our tribe, frightens us. They are a threat to what we think is the right way of life. We fear how they make us feel. A lot of this, too, is taught to us. Little babies aren’t alarmed by any perceived “differences” among people. They will smile at a an unkempt beggar and equally smile at a well-groomed socialite.