American hero Lenny Bruce would have had plenty to say upon this subject.
Before we go any further, I would like to point out that it gives me no pleasure to hear the word nigger used gratuitously. I do not want any of the black people who play this game to mistake any of us for racists.
That being said, I tend to resent most aspects of the politically correct movement. You ask why the use of certain terms is inherently racist? As you suggest, it isn't.
But language tends to follow hegemony. And hegemony tends to follow power. The cheerleaders of the "Politically Correct" movement draw attention to various terminology not because they seek to amend errors in our social customs, but because they wish to stake their claim on some elements of power.
Simply put, if someone has the ability to decide what language you are and are not allowed to use, that person has a limited sort of power over you. Perhaps more importantly, when they are able to label you negatively, perhaps as a "racist" for failing to follow (even accidentally) their prescribed speech patterns, they achieve a much greater sort of power.
These actions are, in my opinion, more likely to contribute to the underlying social problems rather than to ameliorate them. Especially if you believe, as I do, than polite candid and frank dialog can potentially contribute more to reducing ethnic or sectarian tensions than the establishment of a body of taboo.