They invalidate the rule 'ALL Nazis are bad' - I have it on good authority that almost all Nazis were bad, but that is not quite the same thing. This is the nuance bit. Because whilst Rabe may be the exception to the rule, it is this exception into which thought must go. Whenever people say 'ALL X is Y' that needs to be a definite, because generalisations and a lack of questioning are the lifeblood of a demagogue. :o)