We like our identities to be enduring, stable, and constant. The best description of this is ethnicity. When one of our major in-groups becomes ethnicity, we face the danger of developing racial prejudice. The United States is unique in that most races do not solidly identify themselves with regions of land and religions, but in other countries oftenthis is the case and it can lead to major tensions. For example, Israel and surrounding countries have been the scenes of countless battles over Holy Land.
Groups feel their identities being threatened and react in fear and violence.
We seem unwilling to look at our enemies in as people and not faceless forces. We seem to view people that we don't have connections to as more similar to each other than those that we do know. When we were young, adults all seemed to blend together, but our peers jumped out at us as specific and unique people. This is an example about the homogeneity that people see in those that they feel are not similar to them. Racial slurs and prejudice are the products of this unfortunate human tendency.