Calling a black person a nigger is and always has been an instant ban offense here. Same as calling a gay person a faggot or some of the other homophobic insults aimed at them. Other racial / ethnic slurs going into the instabannination box are wetback for Mexicans/Latinos and probably some derogatory names for Asians.
With regard to the word cracker, a bit more complex than ban on sight. We've had some regular members use that term in an ironically self-referential manner and a couple of black members have used it toward white members in a manner of a mild rebuke in a few instances with nobody getting banned and everybody understanding what was meant and a more or less good debate was had by all.
THEN we have the Afrocentrist morons (globalafrikanpower, Mystikal, Louisvilleslugger, Big Triece). Hoo-boy....
- unfounded pseudoscience
- ignoring evidence
- every debating fallacy in the book
- chestbeating internet tough-guy bullshit
- gratuitous usage of the word cracker as a pointedly racial slur
- often gratuitous homophobic slurs on top of that
Yeah, I let those guys unceremoniously have it with both barrels.
You can find some of the best afrocentrist highlights by just doing a forum search for that word. Thanas, I and several other people repeatedly engaged them in debate and right now the official board policy with regard to Afrocentrists is that we no longer even bother waiting for them to start hurling racial insults. It's one warning to stop posting that discredited crap and failure to comply means an instant introduction to Mr. Hammer, Ban Hammer.
I don't remember if we actually banned Big Triece (we did ban all of the others, though), just took to locking and HoSing his posts on sight and he hasn't cropped up since.
So, while it is possible to use the word cracker in a non-derogatory way and avoid getting in hot water over it, it is a very, very fine line to walk and in most cases it is better to just refrain from it because it is all too easy to step on the wrong side of it. At which point you're going to have some fast explaining to do. About the only safe usage would be the jokingly self-referential one and even then it is usually in bad taste if nothing else.