My source was this Roger Kimball article. I just found the book that Kimball references on Google Books and it doesn't seem to contain any version of that quote, so for now I'd guess that your version is more accurate. Ideally we'd want to find the original German version.
I found a site which purports to offer Notebook F, from which the quote is supposed to be taken - the text there reads:
Ich kann nicht leugnen, mein Mißtrauen gegen den Geschmack unserer Zeit ist bei mir vielleicht zu einer tadelnswürdigen Höhe gestiegen. Täglich zu sehen wie Leute zum Namen Genie kommen, wie die Keller – Esel zum Namen Tausendfuß, nicht weil sie so viele Füße haben, sondern weil die meisten nicht bis auf 14 zählen wollen, hat gemacht, daß ich keinem mehr ohne Prüfung glaube.
which appears to conform with the Mautner & Hatfield text....
(Since there didn't seem to be one for this month, and I just ran across a nice quote.)
A monthly thread for posting any interesting rationality-related quotes you've seen recently on the Internet, or had stored in your quotesfile for ages.