In the digital age Hollywood casting decisions leaked from behind closed doors can instantly become fodder for public debate. And when the decision involves race and celebrity, the debate can get very heated.

The online media world has been abuzz with criticism for nearly a month now over the news — first reported by The Hollywood Reporter — that the actress Zoe Saldana would be cast as the singer Nina Simone in the forthcoming film “Nina” based on her life.

Few have attacked Ms. Saldana for her virtues as an actress. Instead, much of the reaction has focused on whether Ms. Saldana was cast because she, unlike Simone, is light skinned and therefore a more palatable choice for the Hollywood film than a darker skinned actress.