Ta-Nehisi Coates has a good post on why, yes, black people can call eachother "nigger" and white people can't. It's the same reason that my Jewish friends can make complain about their cheap relatives, why my female friends and I can call each other "bitch" when not even my closest male friends are allowed to deploy the word, and for that matter why I can't call your mohter "Mom" and you can't call my boyfriend "darling". Context matters. It is not the job of black people to set an example for whites on this score. They are not raising us.

In a side note, he hates white people who use "the n-word" as a euphemism. I have to say, I cringed, because I'm sure I've said it to him. But as far as I can remember, I've spoken the actual word aloud exactly once, when I was in kindergarten, and my mother slapped me so hard that my head fell off and I had to carry it with me to school like a lunchbox for three weeks.

I suspect that most white people who can't speak the dread name aloud, even as an example, have a similar history--an atavistic intuition that lightning will smite you if it passes your lips. But now that I think about it, the "n word" locution is pretty grating. You shouldn't dress up a racial epithet in the kind of cutesy euphemism you use when potty training three year olds.