Most conservative blacks don't use it.
Many young people do use it.
I hear it all the time.
So yes, it is a valid argument.
Yes, perhaps, and NO.
Blacks using the words towards each other in a low class way is one thing. Whites using it towards blacks in a manner to demean and dehumanize a black, or to delegitimize their right to speak out at a comedy club, is a totally different thing. If you don't get that, I can't help you.
The "c" word directed to women evokes a similar response. A Mexican using the word "gringo" to refer to whites, is meant by the Mexican to dehumanize, but most whites don't let it because they could give a rat's ass what Mexican's think. I got called a "wog" on a train by a British secretary type in Europe one time because I have dark skin,and I thought it was hysterical. Someday, blacks may have the same attitude towards use of the N word, but that day is not now. So trying to make it ok by pointing out examples of those who do use it does not work. Two different contexts, two different meanings. Richards' meaning was "know your place in this country, boy".