Am I really going to do this? Am I going to spend time on a topic so far from legitimacy as Flat Earth? Doing so risks affording a tiny bit of credibility to an idea that hasn’t earned it, as if I doth protest too much.

We’ve been told that a vegetarian diet can feed the hungry, honor the animals, and save the planet. Lierre Keith believed in that plant-based diet and spent twenty years as a vegan. But in The Vegetar...