One thing Joan Blake said, about the recommendation for boys and men to reduce protein intake, was that the problem was one of displacement--rather than a criticism of protein foods, she was worried that they would displace whole grains and other crud from the diet. The back door of 'plant-based' diets--if you can't prove that meat and dairy are actually harmful, instead emphasize health benefits of plant foods. Which is easier to do--just compare the effects of fruits, whole grains etc. vs refined plant foods.