Hour 2: Why do we judge an entire group by the worst behavior of a few people associated with it?

Charles Stewart II, 52, of Hammond, Louisiana, was arrested and booked on 39 counts of child pornography involving juveniles under the age of 13. The Tangipahoa Parish Sheriff's Office took him into custody following a month-long investigation led by their Internet Crimes Against Children Unit. Why do we so often judge an entire group by the worst behavior of a few people associated with it? Whether it’s politics, religion, race, generations, or professions, when does criticism become an unfair stereotype?