I think rabbit has a point. But also:

How does stereotyping come to exist? It's not because every person in a particular race does this or a particular race is that. But it's because MANY of them do this, or are that, otherwise the stereotype wouldn't exist.

The bad thing about stereotyping is it's defined to assume everyone in a certain race is the same way and different from all other races, which isn't true of course.

BUT, many people of a certain race are like that, because if only a small amount of people from that race was like that, the "rumor" wouldn't have spreaded nationwide/worldwide, thus the stereotype wouldn't even exist. Stereotyping exists because people have found many people of all different races to be a particular way within their race and then spreaded the news.

Also, racial culture has a lot to do with stereotyping how people of a particular race act.