Or problem is we put people into positions of power who developed their sense of morality at a time when "The Nazis" were still a valid political party and we didn't generally allow African Americans into the military yet.
And in 50 years, we'll be putting people into positions of power who believe something that is a very fashionable idea in 2014. No idea what it will be, but since we pick our leadership from among the elderly, and develop our ideas of what's good, right and proper during our youth, it's inevitable.
Note also, for reference, the "Buffalo Soldiers". They were around from the end of the Civil War (formed in 1866). There were Negro regiments during the Civil War as well.
It should be noted also that the 9th and 10th Cavalry, as well as other Negro regiments existed through WW2 until the military was integrated during the Korean War (considerably before the rest of US society).