Humans had been doing awful things to each other since the human race had existed and in fact that is the default condition of the animal when dealing with none members of the tribe/pack. This is even more true of young males, that is why they had always been consider great cannon fodder down through history by every military that had ever existed.
Now there are plentiful examples of black and white young men viewing members of the other "race" as aliens.
An example of this that come to mind on the other side of the "race" divide is in the last major race riot in California where a white truck drive was drag out of his truck and almost beaten to death for the crime of being white and in the wrong placed at the wrong time.
If memory also serve me correctly it was also mature blacks men who interfere with the beating of this white truck driver.
It is only society conditioning that keep our young warriors age males in check and that conditioning is not perfect to say the least.
The teens gangs problems is another example of this.