That is a completely different context. If there was institutional racism against white people in Zimbabwe I would attempt to explain that in proper historical and colonial context. You are just evading the fact that there is institutional injustice against black people in America and why that is. EDIT: Furthermore, from my experience in Africa, if ANY black man shot a white man in almost any African country, there would be international outrage and the African government in question would do whatever they could to bring the black man to justice for fear that the tourism industry would be destroyed.
That is why I chose that particular country, and not any other African Country. But again, you can garner the same results that occurred by substituting values other than location, and black and white. Of course there is racism in America, and of course the fact that the ruling class, save it's current political leader, marginalizes black people. You don''t go from rolling children's heads down the side of a temple, to slavery, to marginal equality, to equality, in a day, or even thousands of them apparently. I still think it is less of a direct issue with color and more a direct issue with the psychology of the person, or people.
The point is that this is not one isolated issue. This keeps happening because there is a cultural sickness in America that demonizes blackness. This has an important socio-historic context, which is what the article is about.