Urban blacks are actually very underrepresented in the military. The biggest overrepresentation is among small town and rural whites.
I just read a report that says exactly the opposite. The military has far more blacks and hispanics than are in the general population by percentage. Whites are underrepresented.
But you don't have to be a high school grad to enlist.
In many American cities, only 50% of African-American students graduate High School.
I'm HIGHLY suspicious of that DOD website.