This is true enough, but the raw numbers ignore the historical changes that occured and also the reason why. In the early years of heavy U.S. fighting in Vietnam (say from 1965-1968), African-Americans were heavily over-represented among both the troops and the casaulties: figting and being killed at twice the rate of the percentage in the overall population. This led to huge outcry among African-American leaders, who joined the anti-war ranks much earlier than most of the traditional liberal-democrats. It was partially to defuse these critiques that Nixon ordered the army to stop using African-Americans as cannon fodder, which brought their death numbers down to the same rate as the population -- think of it as a type of "quota" for deaths. I think George Herring discusses this in his history of Vietnam war. I'll try to look it up.