I can understand why some black people use the n-word though it causes great discomfort to others. They are trying to turn the insult around and reclaim the word, the way that the gay community is trying to do with some words that were used against them in a derogatory way.
I do not know if the attempt to reclaim the n-word will succeed or not but I personally have never used the word and have no desire to do so. But periodically one hears people who are not black complain about the fact that black people can use the n-word with impunity while if they use it they are considered racists. They say this with a sense of grievance. What I have never understood is why they want to use the word in the first place. There are plenty of other words in the English language.
Cartoonist Keith Knight has his own theory about this strange desire that makes a kind of sense though I doubt that it is the only reason.