I often heard the "all black people look alike" line growing up, and having classes in grade school with several blacks, I understood it completely. The only problem was, the majority of said black students were related. They were cousins, all sharing grandparents who had about a dozen children, and their children followed with not-as-large-but-still-large families, all of which stayed in the same neighborhood. Naturally, they shared a lot of features, but I noticed that there were other, white families, who had a similar story. Of course, the members of each of these families were said to all look alike, and no one was saying all white people look alike. My mother had seven brothers and sisters and shockingly you can tell they are related.
My point, if I can be brief, is that while it's an almost extinct form, it's still racism and can be cured by only having basic slight observational skills.
Laurence Fishburne (left),
Denzel Washington (middle),
and Samuel L. Jackson (right).