NEW YORK — At the new Broadway production of “Parade,” the customary recorded admonition to silence cell phones is delivered by no less a personage than Raphael Warnock, the U.S. senator from Georgia. Clearly, that’s an effort to acknowledge that while this somber, gorgeously scored Jason Robert Brown musical is about the prejudiced 1913 murder trial and subsequent lynching of a Jewish man, Leo Frank, in that Peach State in 1915, everyone involved knows that it was Black Georgians who were far more likely to suffer that fate. And, of course, it’s also a tacit statement that the racist forces...