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.