Barnstorming on an Invisible Segway

I could well be wrong - I wasn't there. My source is a Molly Ivins story about John Henry Faulk and J. Frank Dobie, who had grown up hearing polite people say "nigra" and who, on being about to go study outside the state of Texas and having heard that polite people elsewhere said "negro" when they wanted to be taken seriously as anti-racists, solemnly practiced the word over and over so they wouldn't make a mistake and use the wrong word out of habit. Ivins actually spelled it out phonetically, something like "knee-grow".

Could it just be a matter of different accents? (Or, of course, it could equally well be a matter of me being completely wrong, especialy as I'm working from memory and don't have the Ivins book here.)