Because people don't understand that individuals do not represent the whole? Do you make these points just about Americans, or do you use the same logic for ot

Because people don't understand that individuals do not represent the whole? Do you make these points just about Americans, or do you use the same logic for other demographic information? If you see a black man rob a store, do you say "and this is why racist whites hate black people" as if it is somehow a pat on the back for the stereotyping group?