“Today” show weatherman Al Roker is under fire for dressing up on Halloween as Doc Brown, the quirky — and white — time machine inventor in the “Back to the Future” trilogy. Some social media users asked why it was all right for him to dress up as a Caucasian character, while NBC canceled his colleague Megyn Kelly’s show after her controversial blackface comments. “I’m going to say this one last time, but the folks who get it, understand and the ones who DON’T, won’t,” Roker tweeted to explain why his ‘80s-themed costume was not an example of whiteface. “I...