Facebook indulged in a spot of racial stereotyping in its recent television commercial which was dissected in Here Are All the Racial Stereotypes In Facebook's Weird New 'Chairs' Ad. The advertisement "uses a lot of racial shorthand ... Unfortunately, that shorthand indicates that black people like to sit on junky furniture on the sidewalk, while white people lounge in richly furnished rooms."
Of course, some stereotypes are positive, even complimentary, about the particular race or sector of society being pigeonholed. We've probably all heard that Jamaican people are fast runners, Asian people are good at maths and fat people are jolly. (And, yes, "Asian" is a problematic label itself - all but meaningless since it can refer to people hailing from India to Japan and everywhere in between.)
Why stereotypes are bad even when they're 'good' debunks the myth that propagating stereotypes about a particular positive attribute or skill is harmless. Lazy generalisations such as "black people are ... better at sport" or "women are more in touch with their emotions" are considered every bit as unacceptable as derogatory racial stereotypes.
As discussed in The Guardian article, positive stereotypes can "fly under people's stereotype-detecting radars". A reader called ystar perceptively commented that positive stereotyping can effectively "groom the audience", laying the foundations perhaps for less complimentary sentiments to follow.
Evidently, research has shown that "the positive stereotype seemed more likely to lead people to believe that differences between blacks and whites were biological in origin." So in accepting even seemingly benign observations about a particular group of people we are establishing a real sense that these fellow human beings are quite different to "us".