For The Atlantic the distinguished linguist Geoffrey Nunberg has produced an article, "When Slang Becomes a Slur," about the controversy over the name of the Washington Redskins.
Don't pass over it without clicking. It is a thoughtful, substantial article that moves from the controversy over the team name to a deeper understanding of the interplay between language and culture. (You'd be better off reading that than this.)
Mr. Nunberg looks at a number of derogatory words that used to be in common use but which over the past half-century have come to be shunned as unacceptable for public discourse, and labeled as such in dictionaries.
Here's a salient paragraph: "That all started to change in the '60s, though it took dictionaries a while to catch up. The sea change in social attitudes that led to the civil rights acts of 1964 and 1965 also transformed the way we talked about race and ethnicity. That was when we collectively acknowledged that every group was entitled to control its own linguistic destiny, and decide what it should and shouldn’t be called—that groups had the right to define themselves."
One consequence of this sea change has to do with what can be said inside and outside such groups. It reveals a misunderstanding of the new conventions to say, "Why can't I use those words I hear [blacks, gays, women, whomever] using all the time?" Slurs have become proprietary.
A somewhat more innocuous example than anything blacks/gays/women/whoever use is that I as a native of Appalachia can use cracker, hillbilly, hilljack, and related terms as part of group self-identification, but you would be ill-advised to apply them to me. You're not a member of the club.
All this is what quivering wattled types complain of as "political correctness." And while there are examples of political correctitude carried to a ludicrous extreme (differently abled for disabled never caught on), the underlying cultural development dates from the Sixties, the decade the quivering wattled types most despise.
Once the right of groups to define themselves linguistically was established in the culture, multiculturalism, that thing despised as much as political correctness, was a fact, and a source of deep discontent to some.
In American culture, white has been the default. In newspaper, magazine, and online journalism, the governing assumption is that anyone being written about is white unless otherwise identified. You may see a references to "a 38-year-old African-American man," but you are much less likely to see "a 38-year-old white man."
In fact, for a long time in American culture, white male Protestant was the default, although in the twentieth century Roman Catholics and Jews were grudgingly granted admission. Look at the composition of the United States Senate, the boards of directors of the major corporations, or the people around the table at the afternoon news meetings I've attended over the past quarter-century.
Now we can see why something of such slight consequence as the name of Washington's NFL team (I had to use it once to establish context but won't again) stirs up such a brouhaha. To acknowledge that the name is a slur and discard it would mean, in effect, accepting the demographic, social, and cultural changes associated with multiculturalism and political correctness.
It would mean admitting that the white male Judeo-Christian pattern is no longer the American template, but an American template. And folks have been resisting that admission since the Sixties.