During my first enlistment in the Air Force, an acquaintance made the statement that blacks weren't as intelligent at whites. I disagreed with him and he asked if it required high intelligence to get into an electronics career field -- mine at the time. I said yes and he asked if I knew of many blacks in electronics career field and I did not. He said that proved his point. I still did not agree with him but had no facts to argue against him.
Several years later I was in an advanced electronics course and there were blacks in my class and they did as well as anyone.
I then realized that it was a lack of advanced mathematics that was needed to get into electronics career fields, not ability that limited the number of blacks before.