It should be acceptable for anyone to say the word quite frankly. Anytime I hear an black person say "you have no right saying that, that's OUR word" I just want to slap them upside the head and say "You don't get a monopoly on certain words mother fucker, it doesn't work like that". The offense of such a word or any word really isn't on the word itself as it's the context the word is used in. Whenever I say it (which is A LOT) I never mean it in a negative connotation, it's usually just use it in slang to refer to a friend which is pretty much the only way I see it used these days outside of a few incidents. Another example would be the word gay, it can be used in many different ways and most of them aren't derogatory, why is it your problem if someone gets offended when the word is said?
The way I see it unless I'm using the word to attack you or someone you like/love personally then you really shouldn't get upset when the word is used and even then I would suggest not to get too upset about it either. Working on Indian reserves as long as I did I lost count on how many times I was called a Honky/Cracker/Whitey in a derogatory manner, it happened all the time but I'm not going to get offended and get my undergarments in a bunch, life's too short for that shit. Frankly if I'm the one getting bothered or offended by those words then I should probably take a hard look at myself and understand why those words bother me and try and fix that on my end.