Apple has rejected issue #10 of Jason Aaron and Jason Latour's Image Comics series Southern Bastards from its store, and odds are it isn't because of Latour's widely shared essay about the Confederate flag in its back matter.
The likely reason is an explicit sex scene that opens the issue. In virtually every previous case of Apple rejecting specific issues of comics, it's been over sexual content, not language or violence. (The one possible exception is the Johnny Ryan library of comics. It's hard to know where the offense was there.)