Why is the addition of "n-word" as a keyword NOT being accepted

There are 512 titles with this keyword, but, when I recently tried to add it to Lincoln (2012) and 12 Years a Slave (2013), where it is spoken by a character on screen, the additions were rejected. I take umbrage if IMDb is assuming that I, as a contributor, am submitting this keyword from a personal, prejudicial point-of-view.  The only time I can ever remember personally using this reprehensible word was in a role-playing capacity in a graduate semantics class.  I only submit it as a keyword when, as I said, it is spoken by a character on-screen (or perhaps in on-screen text).