Not everybody finds the word Ni gg a offensive. And herein lies the problem. What is offensive to some, is not offensive to others.
You can't just "eradicate" a word because you or the majority don't like it.
Where the word originated from might be offensive, but there is a reason the word exists.
Words will naturally eradicate themselves if society feels they are no longer needed.
Look at slanguage.....it is a very "era-driven" thing. How often do you hear the term "groovy"? It's not in style anymore. Although I hope it makes a comeback.
When enough people get tired of the term n I gga, we will see it less and less.