Are you suggesting that the content presented in http://en.wiktionary.org/wiki/nigger or another dictionary's "nigger" entry is comparable (or could be comparable, given revision/expansion in accordance with the publication's standards) to that of http://en.wikipedia.org/wiki/Nigger ?
It isn't comparable. Could it be comparable? I don't know.
By the way, how does that article and the article on [[black people]] not violate "Articles whose titles are different words for the same thing (synonyms): are duplicate articles that should be merged."
Because one of the unwritten exceptions to the guideline is that articles on terms which shouldn't be used in encyclopedias (without the quotation marks or italics) don't count.