the N - Bomb is that most delicious of tricks, NIGGER. A word which will land a white person in a whole heap of trouble in most civil societies because quite frankly, we need to apologize constantly for using the black people that black people sold us all those years ago. Truly, my bad.
Societal reaction: "WARNING, citizen number 002-75-6343 has used the N - Bomb. Citizen will be sprayed with corn paste and thrown in a pit full of niggahs."
African American says to another African American: "What's poppin' my nigga?" That has become acceptable in society. Puerto Ricans even use it to refer to themselves. That's the N - Bomb in a nutshell.
Use of this term by such dark skin individuals toward others of similar heritage is sometimes thought of as acceptable. Doing this however keeps the word in circulation and promotes the use of the N-bomb by people of any race.
Just to recap what his friend said the white guy also drops the N - bomb:
Hurry up niggaz--we're going to be late!
Then the scuffle ensues.
Moral: if you are offended when anyone uses the N-bomb toward you; don't use it toward others.