I'm sorry if that was not clear from my original comment.

Bitching is the (sort of) equivalent of the word niggardly. Niggardly has no etymological roots with nigger, but they sound similar and niggardly means stingy/miserly/has negative connotations. Lets pretend for a second that they are derived from the same root (They're not but I lack a better example off the top of my head).

Saying black would not be the same as saying niggardly.