I do not feel unbeatablec is a racist, just a 14 year old who made a poor atempt at a joke. To me anytime you refer to a group of people in a slang type matter you could be offending someone. I do know people who would are offened by the term "redneck" which has been posted in the same thread unbeatable posted his slur.
I am only aware of this incedent, but I am sure there are others that also led to his dismisal. I do however feel sorry for him, from the content of most his posts I feel he is craving attention, which makes me wonder about his home life.