I love Facebook, and believe the conversations you can find there to be a pretty decent cross-section of human thought patterns. A conversation yesterday exhibited every one of the following traits, which I think are essential to the maintaining of prejudices.
1) Make a blanket assumption about a group. (“X’s are Y”)
2) When you meet a member (evident or self-declared) member of the group whose behavior violates that assumption, discount it, saying that they aren’t really an ‘X’. (“You don’t behave Y, so you are not an X”)
3) Believe that you, as an outsider, know more about that group than actual members thereof. (“I work with X’s/have studied them/my best friend is. Let me tell you about X’s…”)
4) Deny members of that group the same right to define you. (“How dare you tell me what I tell you…)
I’ve seen people do this with issues of race, gender, politics, and religion. It works!