In what scenarios are white people turning "cracker" or "devil" into a term of endearment and when are half-black rappers being called "cracker" or "devil" to the point where they'd want to own it. If that were happening, then I'd be curious too.
As far as white rappers using a derogatory term to refer to themselves, I'm pretty sure that Bubba Sparxxx and Yelawolf have referred to themselves as "rednecks" and "hicks" in their lyrics, respectively and they've probably been referred to derogatorily as "rednecks" otherwise.
Just seems to me that people take derogatory terms that people aim at them and use it on themselves. Kind of like how it's derogatory to call a woman a "bytch", but female artists refer to themselves & their friends as "bytches"/"boss bytches/bad bytches" or trap rappers call themselves "savages" and "goons".
Lil' dikky's Jewish and refers to himself as a "kike" in his new single.
Macklemore with the "Damn, that's a cold-ass honky" line was pretty big.