Buddy you have a lot to learn about the human body and what it's necessities are. Animal meat is NOT necessary for proper human health. Humans are NOT CARNIVORES. While it wouldn't hurt to eat RAW meat on occasion, our bodies do not require it.
You claim these vegans have Zero muscle mass, Zero energy and are terribly unhealthy...?? Wow. Complete ignorance. Aside from the obvious, even if these people were unhealthy, the fact that they don't consume meat is not the culprit. Most people are unhealthy. Even most vegans are unhealthy. But Meat-eaters (human) are usually more unhealthy than than vegans. Cooked meat is terrible for human body. It renders the meat very difficult to digest and mostly toxic to the body.
And in regards to vitamin deficiencies: Green plants have plenty of Vit B12 in the amount the body requires. Yet another lie that is fed to you that won't get enough B12 if you don't eat meat. And if you eat healthy, then your body doesn't have such a tremendous need for B12, as it does for most in this day and age.
And Vit D! The sun provides your body with ample Vit D as long as you don't avoid it because of the false scare of skin cancer with a little sun. The sun is necessary for good health. Your immune systems suffers without enough sun, for just one example.
And Fat! Do you live in a cave?! There is a truth to all the studies done on saturated fats! The only thing- is that EVERY study was done on ANIMAL SATURATED FATS! NOT PLANT Saturated fat! Animal saturated fat is Terrible for you. In contrast, Plant saturated fat is vital. Coconut oil and Palm Oil are the healthiest oils on the planet- greatly because of their saturated fats, among many other awesome benefits. These plant fats actually IMPROVE cholesterol and the heart and arteries, contrary to what "big money" wants you to believe.
The fact is, most people don't know that what they are eating -in today's toxic world- is laced with so many chemicals, toxins, and pretentious claims to be a healthy choice. Just because someone's vegan, doesn't mean they know what foods to buy to avoid toxicity and bad health. Even most "health" foods today are unhealthy. It's any wonder the human race is still going with the food that is provided to us. Our bodies are struggling to survive. This is obvious with unprecedented amounts of disease. Possibly the only way to achieve great health is to farm all of your own food on organic soil.. and not let companies (who have a profit to worry about) intervene.