Used in a Derogatory or Joking Manner?

As a child, most are taught that there are some words that they might hear around them that are not appropriate to use, from words like "stupid" to simple expletives.  For example, everyone in my family knows the story about how my uncle used to tell his big brother and sisters that "Stupid's a naughty word".

However, everyone has their own idea of what sort of language is acceptable.

In "A Raisin in the Sun", Lorraine Hansberry employs the "N" word multiple times.  Now, every critic has their own idea about this word being used in literature: some think it should be taken out, others think it should be censored, and many think it should stay in the literary work like it originally was.

The thing is, African-Americans call each other this frequently, so why is it socially unacceptable for people from other races to call them that?  If they found it that offensive, NOBODY would call them that even if they were also from African descent and using it in a joking manner.  I don't mean to affront anyone here, however it seems hypocritical to me for whites to be criticized if they were to use a word such as that.

There really is no definite line between joking around and actually trying to offend someone by using that word.  So what's the solution?  The best thing to do would be for everyone to refrain from using words that most people would find offensive, leaving the world a much friendlier and positive place.