What if a black person says "To all my n*ggers out there, x,y,z" on twitter, vs. a white person saying the same thing. Will the white person's tweet be removed, or both?
Interesting point. How can anybody know? If I have a penis, under today's standards I can claim to be female. If I have caucasian ancestry, can I claim to be black? Why not?
Because all of these factors will necessarily have to be taken into account when we come up with our speech rules, don't you see?
Sure it's complex, convoluted, and controversial.. but as long as we put the right people in charge to make the decisions for us, it will all work out fairly.
"We", meaning the readership of this site probably doesn't (I hope?), but it is a common trope that what you are allowed to say (meaning: be accepted without immediate backlash) is based entirely on your identity.
I'll not go into that concept further for fear of igniting another tired flame war.
Don't forget that there's a vast number of African Americans who do not condone the use of the n word freely and for fun as it happens these days. I believe their main objection is that it takes away from the meaning and history associated with it. If we consider another N word (Nazi), then it's also use popularly but only to mean something very negative and not in the sense of "my buddy".
The meaning of speech depends on context, always. If I say something by myself, in the privacy of my home, it's much different than if I say the same thing with a microphone to an angry mob. Yelling "fire" when a building is on fire is different than yelling it in a crowded theater where there is none (a classic example from law).
Similarly, if a white person publicly says something discriminatory against black people, it's a much different context than if a black person says the same thing. As an simple example, imagine a two black people in a room of 40 white nationalists: If one black person says to another, "hey n-!", that's much different for the person hearing it than if one of the white nationalists says the same thing.
There's a lot more to that word, including black people taking power for themselves and away from racists by using it (really a brilliant, innovative way to push back), but that's too much to write here and now.