|There is apparently a part of our brain which judges people based
on whether they can be considered somehow "similar" to us. If they
can be considered similar, such people are judged to be safe. If, on the
other hand, they are considered to be "different" than us, they
are coded as dangerous.
This part of the brain developed early in human evolution as a basic self-protection mechanism, and most often we are not aware of its influence on our thought processes.