It is not "censorship" (your word) to recognize why non-Black people shouldn't use the n-word, nor is "apartheid" the appropriate way to describe how we challenge racism differently depending on how we ourselves have been racialized. When the speaker is Black, the n-word slur has a particular context and can convey different meanings than when the speaker is not Black. Black authors have written a lot on this topic. See, for example, a 2008 book The N Word: Who Can Say It, Who Shouldn't, and Why by Jabari Asim, former editor-in-chief of an NAACP magazine. Here, the "shouldn't" will of course be Asim's opinion based on his deep knowledge of the topic, not a writ of government censorship.