A new book comparing Melania Trump and Michelle Obama has brought out predictable slaps against the current first lady from bullies who seek to attack the president through his family. Pitting two women against each other just never gets old, does it? “Melania & Michelle: First Ladies in a New Era,” by Tammy R. Vigil, is presented as a mere bipartisan assessment of the public images of both women. But it thinly veils its criticism of one and its admiration of the other. No prizes for guessing who’s who. Vigil, a Boston academic, notes that Melania “ranks among the least...