Discrimination is a basic human fact.  The ability to discern between all things we are able to perceive and determine if they are good, bad, or irrelevant is genetically programmed from birth.

How we react becomes a learned activity over time.  Initially, our discriminatory behavior is rationally individualistic.  Rationality though is somewhat subjective.

Racism

Racist behavior is typically learned not inherited except where a personal need drives our behavior.  That is a mix of genetic and environmental drivers of racism.

In the case of basic human behavior, if it is to our advantage to, for example, bully someone to satisfy a need (either power or physical possession) this is not necessarily based on something we have been taught.

Social Pressure

Another powerful influencer of our behavior is social norms.  We are taught to believe that the group practice is correct and personal consequences of deviation from this form of groupthink (illogical as it may be) can be negative.

Like sheep, we follow the herd faithfully.  This can be true even if our personal beliefs are not aligned.  There is some safety in being aligned with the crowd.  Of course, if the crowd is against you that is something else entirely.

Rational Individualism

Following our own path applying logic and rationale can overcome the failings of being a cog in a large group wheel. Unfortunately, though strident individualism goes against humans’ basic nature, this is the need to integrate, which grows stronger as we mature.

The difficulty of going your own way, and doing what is right in the face of false learning and group pressures is not easy but can be very rewarding.