Most of the modern "fad" diets are against dairy. Personally, I'm torn. I'm half-convinced that it's "unnatural" for human consumption, but at the same time it's a cheap, tasty way of getting good fats and protein.
Its not like a large portion of the Earth's human population has evolved the ability to process lactose after childhood or anything--
I can't speak for the specific case, but on a general guideline, the great majority of people can reap huge benefits simply by doing sports and dropping junk/processed food. In this perspective, choosing one food [group] over another, is nothing else than bikeshedding (in other words, the bottleneck is somewhere else).