Prejudice is disliking something or being against something for irrational reasons.
Frequently people become the victims of prejudice because they belong to groups that suffer prejudice. White people too often look down on Black people for no good reason. Men sometimes look down on women and women sometimes dislike men for bad reasons. Rich people too often look down on poor people and also blame poor people for their misfortune. Poor people and people with average incomes blame rich people for being selfish. In many cases that selfishness is Objectively true, it's not prejudice. There are a few rich people who try to use their money responsibly and we shouldn't look down on them.
In many nations foreigners and immigrants are the victims of prejudice because they're not like us. Still when we go to other nations we become foreigners and we don't like it if the people in those nations turn against us because we're not like them.
The tendency to blame the victim reflects the way Human societies encourage the psychological construction of the OTHER to alleviate guilt. In bourgeois societies ordinary people are encouraged to blame Other races, foreigners, Immigrants, Poor people while selfish rich people work to keep those who might oppose them divided. Among Communists the Bourgeoisie, the Capitalists, a range of Class enemies are blamed for what's wrong in society, especially Poverty.
If we ever contact Intelligent aliens some of us might become prejudiced against them because they will certainly be very different from us. If the aliens are stronger than we are and technically more advanced any prejudice could be dangerous for us.