Your post doesn't really make much sense. If you mean to be offensive there is no reason to say N-word instead of the real thing. Standing in public shouting N-word is likely going to be just as offensive as using the real thing so you might as well use it. The reason it would be as offensive is that shouting anything in public in that way is offensive.
On the other hand if you are trying to be offensive, calling someone an "N-word" might get the reaction you are looking for, but it might just get you laughed at. What it won't be is politically correct.
The reason N-word is used instead of the real thing is the same reason F-word is used instead of the real thing. To avoid needlessly exposing children to the word, even though most kids above the age of ten know both already, still it's best not to encourage them to use them. It has nothing to do with political correctness. It's something people in polite society do as a courtesy.
You do understand sarcasm?
As in: Sarcasm is a form of speech or writing which is bitter or cutting, being intended to taunt its target.?
I give up.
Some people will be offended if you hung them with a new rope.