Im quite aware that there are different folks that see the word differently. I dissagree with why Icecube and that particular set of people think that they have some right over a word and are able to use it but others shouldnt. I have a right to disagree with that. Who am i to tell another person they cant use a word in the same context as someone else because of the skin color. Why can a Black man grown up in a white household in lets say North Dakota say the word but a white man that grew up in for arguments sake compton with predominantly black people and grew up in that culture not say it. The reason that is given is in my opinion silly. Either no one says it as its deemed offensive or anyone can say it in a non offensive way. And I disagree that all 3 different types have different upbringings and life experiences. And for your information i am quite aware that black people arent some homogeneous block. No race is. I would never think that as i know first hand
If you want to be that pedantic, then the reason behind it is linguistic & pragmatic.
The use of words or phrases by 'others' who aren't part of your group aren't seen as familial/warm/inviting depending on your relative status & proximity to the group in question, even if your intention behind saying it is pure.
Relative status as a circumstance for speech reigns even truer when it comes to words with a history of derogatory associations attached to it.
For example two gay males may jokingly say to one another "shut up fag", and not take offence. Now a heterosexual male does the same thing to a gay male, and they're more likely to take offence, or at least feel defensive. Not the best example off the top of my head but you get the idea.
Everybody will have different opinions on the appropriateness, some will feel that members that aren't part of the targeted group shouldn't use the word. Others will feel that nobody should use the word at all, some will allow for people to use the word if the intention behind it is not meant to be offensive.
But ultimately, not one person's individual opinion (not mine, not yours, not anybody else who may be reading this) has any authority over the other.
I'm not going to go into the specific semantics behind n*igger & why this particular word has such strong emotions attached to it, everybody has google.