While a lot of blacks use the N-word, check out Russell Simmons Def Comedy Jam on HBO and you'll be shocked at how much they drop the N-bomb, the explanation as given to me by several people of color, and from some interviews with notable black celebrities, is that they don't view it as derogatory amongst themselves. The word "themselves" however doesn't apply to all black people since many of them still abhor the word, see Bill Cosby. However, within the Black culture there has been for a while now, a large number who use the word as a term of general recognition which expresses the exclusive "bond" amongst them much the way surfers might call each other "Dude."
This confuses many white people who don't understand the context in which black people use the word. It just seems crazy to them that black people would use a word which signifies so much hatred towards their race and serves as a reminder of centuries of slavery/bigotry to us. Other white folks wonder why they can't then use the word right along with them, especially if there is a friendship between them. While I have heard of a few instances of blacks allowing whites to use the word in that familiar sense it is largely considered a no-no for whites to use it and I've seen first hand the results of white, Eminem wanna be gangstas trying to use the term as if they were black themselves, its quite a bloody mess. I heard one black comedian explain it by saying "Don't bother asking why, its just the way it is." Without coming to a conclusion as to all the reasons why, I think it suffices to say that there are probably several reasons why they use it but don't want us too.
In Richards' case while I found his comments offensive, I think he resorted to them because he simply couldn't handle his emotions the way a great comedian should be able to. Richards was simply ill prepared for the situation and thats quite troubling since anyone pursuing a career in stand up should have been aware that hecklers do exist. However, I also found the recording of the incident to be troubling as to the response he got from the hecklers.
They can clearly be heard on the tape calling him a "Cracker Ass cracker" in addition to something else about being "...white...". My own opinion of the matter is that it is no more acceptable for them to respond with racist remarks than it was for Richards to do so. Ideally you want to rise above situations like this, not jump in the toilet with them.
Before sinking into grade school logic like "he said it first" we should ask ourselves, does someone else saying something offensive require an equally offensive response back? Does it make anything any better? Does it solve the problem? I think not. My own opinion of the matter is that Richards was wrong to say what he said but he was provoked by those people and no one should ever assume that when you intentionally get on someones nerves that they will react civilly. It takes a tremendous amount of self control to ignore a Douche bag who won't stop hounding us, let alone be civil with them!
Thats not to say that "they had it coming" either, just that they did something they knew was irritating and they got a response they weren't prepared for. Its much like walking into a bar and seeing someone you don't know who is singing karaoke and telling them that they suck only to realize that they are a street brawler as they come flying off the stage to knock your teeth out. In short, it doesn't pay to be a prick to people you know nothing about and if you choose to do so then you invite an uncertain response, whether right or wrong, which could range from laughter to a kick in the throat.
I believe the best response in this situation would have been to complain to the management, walk out, and alert the press as to Richards going off the deep end. To sit there and make racially insulting remarks of their own accomplished nothing other than to show that there is still a racial divide amongst many Blacks and Whites in America who we would never guess held those kinds of thoughts in their heads only to realize it when there is a confrontation between them and people of a different skin color/religion/gender/sexual orientation when inflamed emotions bring all that garbage out.
I don't know if Richards is a racist or just totally lost his mind for a minute but its sad that he resorted to racial terms to deal with the issue, what if the hecklers were white? Would he have called them "honkys" or "crackers"? I see people every day however who are just like this, always friendly and polite to "different" people but as soon as they are alone amongst their "own kind" they think nothing of letting epithets fly under the guise of a "joke" or "just guys talking" and when questioned about it respond they "don't mean anything by it." The thing about that kind of thinking is that its a slippery slope which once you start going down is hard to stop and eventually will end up embarassing a lot of people.