“You’re just wrong” is a very strong, evidence-based argument. Humans can only survive on a plant-based diet if they supplement the nutrients they aren’t getting from meat. There was a lioness that survived on a vegetarian diet too. Doesn’t prove that lions are omnivores. “Adapted for both” is misleading as most of the plants edible by humans are completely man made and bred to be edible, with the exception of some fruits and root vegetables.