For those individuals who have power, this can lead to their engaging in discriminatory and racist practices.
Not everyone, even if they are the same race, is the same.
Basically, even though positive stereotypes seem like compliments, they can actually lead to negative judgments about the target group and even discrimination, which is why they can be so damaging to society.
Now, before anyone comments on the tone of my comment as opposed to the content of it, I just don't see the point of examining stereotypes from a clinical and pc point of view.