The 90% figure has *some* factual basis.
I bought the "World at War" BBC series box set (great old show from the 70s that scared the hell out of me as a kid, with its flames-and-doom opening sequence, "Russian funeral music" musical theme) and the 90% statistic was also used. I believe the number derives from 90% of the vote Hitler got:
Hitler Endorsed by 9 to 1 in Poll on his Dictatorship, but Opposition Is Doubled
New York Times, 19 August 1934
Berlin, Monday, Aug. 20—Eighty-nine and nine-tenths per cent of the German voters endorsed in yesterday's plebiscite Chancellor Hitler's assumption of greater power than has ever been possessed by any other ruler in modern times. Nearly 10 per cent indicated their disapproval. The result was expected.
[...]
http://www.hartford-hwp.com/archives/61/198.html
Of course, I dunno how many stayed away from the polls, or if they were rigged, or what.
-B.
Chris Doss wrote:
"Riefenstahl (who looks damn good for a 90-year-old) claims repeatedly that 90% of the German public supported Hitler and she was just part of the era, and so on and so forth. 90%!?!? I know the NSDAP led a mass movement and all, but this seems like an exaggeration to me. How much support did they actually have?"