The narration in Al Kafi is graded by Al Majlisi as mursal i.e. has a disconnected chain of narrators, and therefore is not reliable.   Besides, one important way of authenticating a hadith is comparing it to the quran. Since racism goes against the quran (verses like 49:13 for instance), no narration that discriminates like this can be relied upon, even if its chain of transmission was seemingly reliable.