Debacle? Because one idiot wrote an article about it?
I don't think there is any stock answer to your question, it will always depend upon the show, the actor, the director, the concept -- and of course the audience's willingness to suspend their disbelief. (Although, in general, I think the sexuality question is just as ridiculous as suggesting that only people diagnosed as bi polar should play bi-polar characters.)
People were aghast when Phylicia Rashad (sorry if the spelling is wrong) was color blind cast in August:Osage County. Most people here thought it was a horrid idea. Most people actually SEEING her performance thought she was wonderful and got past the race difference.
Personally, I think there are very few circumstances that can't work. The only ones that spring to mind would be (as has been said here in numerous discussions on the same topic) topics that are ABOUT race. How would a color blind cast work in Ragtime? In Once on This Island?
If we're not having fun, then why are we doing it?
These are DISCUSSION boards, not mutual admiration boards. Discussion only occurs when we are willing to hear what others are thinking, regardless of whether it is alignment to our own thoughts.