I am not sure what a 'professional historian' is, or how this would downgrade an individual if his work is expertly researched, documented, respected, and referenced by academics and amateurs, alike. Do you discount Dave Powell's work?He has a BA in history, but he has a 'day job' outside history, so he might be a professional something else. What aspect of Rhea's work - besides labeling - lowers his status as a historian? Gary Gallagher is incredibly entertaining, does that make his content any less factual or compelling?