Well, the standard definition of "Black" in the US has been, more exactly, "at least part Black" ever since the abolution of slavery.
While in Jamaica, people as white as Colin Powell, Bob Marley or Barrack Obama are, in everyday speech, referred to as "Whites".
That definition of "black" was designed by virulent racists who considered a person with any black lineage at all to be contaminated.
And yet this definition has effectively been embraced by many blacks themselves and those who claim to sympathize with them.
A big part of the problem with the current "civil rights" movement is that it is composed of very small minds, unable to really think beyond the patterns of the past. They simply repackage the ridiculous old thinking in a slightly different form, and think that is the answer to their problems. In reality, they have only succeeded in perpetuating the problems.