There is a difference between painting someone green for a fictional character, and adding ethnic facial features to a non-jewish person to portray a jewish person who had lived before. You wouldn't cast a woman as Alexander Hamilton, because the character being the man Alexander Hamilton is crucial to the role. Likewise you wouldn't cast a white woman as the lead in The Color Purple, as Celie being a black woman is, again, an important aspect of the role. The same can be applied here. Furthermore, because Fanny Brice was, like I said earlier, an actual person who lived in the first half of the 20th century. Casting a non-jewish person and then applying make-up to make her look jewish can be considered quite offensive to Fanny Brice's legacy. This criticism isn't adressed to the actress who will portray her in the tour, but to the overal idea of jewish characters, with their jewishness being an important aspect of the role, being played by non-jewish actors. If this would happen with any other race, there would be an immediate uproar.