I think that noted athiest Ricky Gervais said it best:
Just because you can be offended doesn't meant you're right.
Personally I think it's a mark of maturity to not automatically become offended when something blatantly offensive is said. I reflect my disbelief back unto the source and ignore any further comments as those that come from a madman. There are classes of people out there who make it a point of becoming offended and using that as an excuse to go on a rant themselves.
'Redneck' is one of those words that used to have a much more sinister meaning, but now is actually adopted by some. Any overtly racial undertones (after all, redneck almost always refers to a white person) have long since vanished. I can perfectly understand how a black or Hispanic person could be called a "redneck". Put on some Wrangler jeans, boots, and a cowboy hat, and you're there. It could be as simple as just chewing tobacco.
The 'N Word' is a bit of a different story. Though many victims of this word have embraced it in modern times, it's just a matter of politeness to not use it if you are not black. Someone calling someone that as a deragatory name rightly deserves to be shouted down. Someone mindlessly repeating the words of a rap song should be politely reminded.
Jesus, now I sound like Mrs. Manners.