well....
I really guess that the insult has to be determined by the 'victim'
I have been called an okie in a joking manner- never really bothered me... but if I was sensitive about it I might be offended- its all in the eye of the beholder. I - being a white male- cannot concieve of a term that would would really hurt me-
but I also understand some words are hurtful to some, so i limit my vocabulary by a few words- I find it hard to say the 'n-word' even when discussing Twain's works. I also have a hard time using the 'redneck' label.
it boils down to respect, you should try not to disrespect people- it is just that simple....
(Of course I curse like a sailor when my laser has a problem, but that doesnt count)