Stereotypes are derived from common, outstanding attributes and behaviour patterns. While stereotypes might be outdated and in some cases oversimplifed, they exist on the basic human need to simplify patterns down to their most basic level. It's a survival skill our ancestors became excellent at to help them identify threats in their environment which has kind of backfired in this modern society.
It is ridiculous to assume people can easily overcome what is part of basic human nature, and still serves some use in today's environment (for example, you probably wouldn't want to walk up to some guy in hoodie brandishing a knife).
i was debating whether to post basically this so i'm glad mcjob did it for me. in truth, stereotypes also aren't always necessarily considered a bad thing, sometimes they can actually be positive and make people more successful (that doesn't make them fair, but it's miles better than having negative stereotypes). but there's a vague point where suddenly you end up in a situation where you're making a lot more assumptions about people than might be fair, and those assumptions, when adopted on a large, society-sized scale, can definitely contribute to very difficult, long-standing problems of prejudice that do, in fact, affect the lives of other people.
wait hold on why are we ignoring the fact that tez's stats say that black people commit more crime and instead opting to argue over how tribal he and his stats are
either because they've decided it's not worth their time to argue with tez about things that seem obvious to them or because we've moved on to other things. probably a combination of both