I'm tempted to say that if anything is an insult to the German language, it's Klaus Fritz' translation (but 'insult' is probably too strong an expression when I'm merely unhappy with it, so let's just do away with that particular hyperbole). Are you by any chance familiar with this site?
Personally, I prefer reading 'Hermione' even in German fan fiction and would use it if I were writing Trio fic, and while I agree that it's possible for an author to be obnoxious about it, I don't see the appeal in pretending that a bunch of people with German-sounding names is going to a school in Scotland. I can see why people would want to maintain homogeneity within the fandom, though.