Answer:
Racism is fear, pure and simple. Any person that fears another person because of his personal characteristics, be it color, religion, or nationality, is prejudging someone else because of something that s/he fears.
The unknown is a powerful motivator. The person that fears any group because they are different than himself is racist. Attempts to dishonor another group because of this fear is baseless and truly ignorant. It is impossible to judge a group based on superficial externals.
Throughout the years, the ignorant have used racism to denigrate black people, Catholics, Protestants, Jews, Chinese, Japanese, Russians, Irish, and Muslims. People are people, we are all the same. Simply because they look different or speak differently, they are discriminated against because of that difference, not for any real reason.
As long as there is a culture where individuals are supposedly part of an identified group that is unpopular, there will be racism. The shallow people who are overtly racist have, for the most part, never engaged the group they supposedly hate. They base their fear on hearsay and rumor, not on fact. In order to make themselves feel better, they try to belittle the group simply because they do not understand the culture or the language.
Racism is ignorance. Pure and simple, a racist has never engaged a member of the group he fears. He fears what he does not understand.