[brlewis]

Bayesian treatment of email examines a large number of indicators (words) and chooses the best ones to make decisions. It can be very reliable. Prejudice works with a much smaller number of indicators (race, gender, etc.), most of which are poor quality, resulting in a lot of wrong decisions.

Stereotypes are useful in books and movies, because they fool you into thinking you have deep knowledge of a character you're barely acquainted with. In real life this is not a good thing.