Agreed. The 'one drop' rule makes no sense.
The sad thing is that many blacks have bought into this. Reminding me of the racial bigotry that is found among minorities. My daughter is 3/16 Native American and got a job as a PA for the movie "Tecumseh." She got it because her grandmother is an Indian and her uncle was almost elected chief of his nation. She does not "look" Indian in the least, so the "real" Indians on the set began making snide remarks about her. But she made friends with a Shawnee chief (who was a mixed-blood himself) and he shut them up. (helps if you are young and cute!). No cure for this stuff: it comes from a feeling of insecurity.