Hell, the Eskimos ate a diet almost entirely meat-based for hundreds of years. It wasn't until they were introduced to fruits that they began developing diseases like diabetes. Steve Jobs' health nose-dived once he switch to the fruitarian diet; research now shows that the fructose and glucose in fruits is in fact the number one preferred fuel source for cancer cells, which is why the current dietary advice is for cancer patients to go on low carb or ketogenic diets.
The greatest athletes in history eat omnivorous diets; during his record-setting Olympics run, Michael Phelps ate thousands of calories of fast food each day. Few professional athletes are vegetarians, and no elite athletes are fruitarians. All of our most famous scientists, including Einstein and Hawking, ate balanced diets that included substantial amounts of meat. The evidence, and thousands of years of human history, speaks for itself.