Why those diseases? Insulin resistance, i.e. too much carb. And if we're frugivore, why can't we digest fibers like herbivores, and our stomach acidity is closer to a carnivore's?
Of COURSE we don't "need" meat to survive. But unless your meatless diet has enough saturated fat, you WILL die before, say, a clean keto eater
RE: Do vegans 'force' their opinions on others?