A Grammar Nazi is someone who makes posts that point out other people's grammatical errors. You attempted to do just that, but you incorrectly corrected someone.
*facepalm* I'm not the one who made it a big deal! You failed, I corrected you, you argued, I explained again, and now I'm the one making a big deal? Anyway, I have the best armatar, considering I can no longer use the black one...