Jeez, some of you are really touchy. Okay, if we want to be really pedantic and purist about it, it's not a Derby.
I, myself, have never called it a Derby, I'm just explaining why I don't think it's so outrageous that some people do call it that. I mean, afterall, the definition of a derby game includes regions and as someone has mentioned, Sunderland and Newcastle is a Derby game, so it's not technically incorrect. I just didn't really like the way people were jumping on that poster who called it a derby, talking down at him from high horses.