A racist is a person that believes races of folks other than the one he/she belongs to are inferior. No true American liberal/conservative believes that only leftist and rightist believe that kind of stuff, because both are mental authoritarians, fascist, socialist & BIG government collectivist.
A reasonable view, but there is actually a more precise definition.
In formal logic, there is such a thing as a compositional error. This is a fallacy (an error in logic). It is improperly extending the elements of a class across the entire class.
An example is a bag of marbles. You pull two marbles out of the bag and they are both white. From this you assume the bag contains only white marbles. Obviously, this is wrong. It is extending a property (color) of an element (a marble) across the class (the bag of marbles) improperly (by assumption).
When the class is people, this fallacy is called 'bigotry'. It is extending some property, such as a religious view, across an entire class of people (that may have many religious views). Religious bigots such as anti-Semites, people that argue all Christians are fundamentalists, are one example.
When the property extended is a physical inheritable trait, such as skin color, eye color, nose shape, hair color, etc. the fallacy is called 'racism'. Racists are also bigots since one is an extension of the other.
This fallacy is a particularly ugly one. It is often used by liberals and socialists to divide before conquering. It also has been used to justify not only simply mistreatment of people, but to justify genocide.
Socialism can only exist by stealing wealth. Those condoning it must declare themselves The Elite in order to specify how your wealth should be redistributed to others. This is the mental authoritarian aspect that you see in them.