Continuing along the same lines as posts 4 and 5, people are afraid of what is different or what they do not understand. Fears may end up as prejudices and bias. From a historical standpoint, prejudice was necessary for the survival of the species. Prejudice is the formation of an unreasoned opinion or feeling. We don't look favorably on most prejudice, like the type of prejudice shown against gays or people of a different race.
Why is there not a word such as postjudice? Some people form opinions after they have had many experiences, but still their opinion is labeled "prejudice" if it does not fit the "conventional wisdom." Is postjudice ignorance, too? Maybe this question does not belong here, but when some people voice their postjudices, these opinions are summarily labeled "prejudice." It is curious, is it not?
As long as there are differences between people there will be prejudicial attitudes. Some prejudices are more socially acceptable than others -- for example, it is perhaps OK to be prejudiced about convicted criminals, while racial prejudice is condemned. I agree with the above posts that suggest that most prejudice is a form of ignorance, and I think that education has and could change a lot of those beliefs, but I also think it is also important to acknowledge that we live a sea of prejudices of all kinds -- some more damaging than others.
This depends on what kind of prejudice you are talking about. Prejudice based on race is, as Post #2 says, seen as ignorance. However, other kinds of prejudice are still seen as relatively acceptable. For example, prejudice against gay people is perfectly acceptable in many parts of society. Mitt Romney faced problems in his campaign for the presidency because of the fact that he is Mormon.
So some forms of prejudice are still quite acceptable in much of society.
In modern-day society, prejudice is equated with ignorance. The common thought is, if someone has personal, racial, or religious prejudices, he or she must be intolerant, uninformed, and consequently, "unenlightened." In truth, psychological research shows that we have innate prejudices, and we simply choose to overcome, ignore, or repress them as responsible members of a cohesive society.
In literature, prejudice is demonstrated and addressed in many different ways: In novels like To Kill a Mockingbird, prejudice is condemned through the events of 1930s Maycomb County. In plays like The Crucible, prejudice is portrayed as the cause of tribulation and wrongful persecution. Authors have used prejudice as a theme and as a device since the beginning of great literature occurred.