The comment regarding how white people can't play roles that black people play, but black people can play white roles isn't racist at all.
Annie Oakley, or Oklahoma for that matter, do not approach the subject of race. Most "black shows" are about black people and are race specefic, and ABOUT black people, and unless the show does not call any attention to race, like The Wiz, or Smokey Joe's Cafe, and the like, then it's FINE to have "color blind" casting.
Big River is NOT a "color-blind" casting show. Unless they reversed EVERYONE, then it doesn't make much sense.
Personally, I think I have too much bloom.