Since DistrictDeacon is either unwilling (childish) or unable (child) to answer my questions, I'll take his advice and answer the most recent one myself. I tend to treat the insult "white bread" in much the same way as "cracker." They share many of the same valences: plain, bland, uninteresting, white. DD clearly doesn't find the former insulting because it is his avatar. I can't remember its genesis, but it seems at least that he has embraced the label ironically. Why is "cracker" any different? Is it because the name-caller was black? Or do you genuinely find the term "cracker" to be derogatory?
Or is "cracker" insulting in this situation precisely because it wasn't punished?
What if she had Photoshopped his face onto a piece of white bread? Would that be just as insulting? Would you still consider it racially motivated?