Keep in mind I do not condone as I find the word abhorrent.
In the football world the N-bomb is ubiquitous. You'd be shocked just how much the N-bomb is thrown around and not just by black players or coaches. In that context, it's not meant as a racial slur and oftentimes is a term of endearment. The football world is very much influenced by the hip hop/rap world where the term is extremely common. Not a surprise as that is often the music you find in the locker room.
I personally made my players run or do up-down when I heard the term. They learned fast. As an official I'd give a warning and then flag.
It's important that you understand context when discussing the term in the football world.