A 1985 Dallas Morning News article attributes the heuristic to "Sanders", as cited in a 2003 mailing list (https://listserv.linguistlist.org/pipermail/ads-l/2003-Septe...).

Fable 5.2 couldn't access the full DMN text (nor can I), but suggests the article is about "local TV journalists reacting to a report on minority hiring" and "Sanders" is probably a reporter named Bob Ray Sanders, a reporter in the region (who was later inducted to the National Association of Black Journalists' Hall of Fame). What he actually said is sadly paywalled in the archives.