Listening to the Radio Today

The topic I bring for this blog comes out of the 'Black and White' lecture and from listening to the radio today!
What never made sense to me in everyday life today is the true meaning behind the word that impolitely refers to African-Americans (Since it is a public blog, I have decided not to write it out).
In discussion, it was mentioned that Martin Luther King Jr. used the word 'nergo' throughout his life to refer to African-Americans. Over time the more 'serious' word of that evolved that today means something degrading and unacceptable to be used in public.
Now, what I don't understand is why this word remains frowned upon (not that I'd personally use it if it wasn't) when used and degrades African-Americans (and Blacks for that manner) when it is used so openly in music videos and artist recordings pretty much all everywhere. It is true that when broadcasting these songs, radio stations either mute or replace the word with something else (in order not offend anyone and remain politically correct) but what strikes me is still the fact it is being used. Strangely enough from what Ive noticed is the artists using this term to refer to Blacks are themselves Black!!

For example: "Old rap" Biggie Smalls feat. 112- Sky's the Limit and in "New rap" Lil Wayne- My **** Lyrics. and the examples are endless because so many more artists use the term.

It just doesn't make sense to me that a word be so bad to use in public by the public, yet the very people that it affects, use it loosely in communicating and in music lyrics.