Absolute propaganda, and mostly bullshit. Honestly one of the worst diets for you is vegan, some people do ok on it, but it's rare. The reason most people feel good at first is that they weren't getting enough vegetables in the first place. Most vegan proteins are not very bio available along with omega 3 and 6 sources. Saturated fats is another issue, which you can get from coconut oil, but saturated fats are responsible for sex hormones. The bottom line is being vegan requires so much supplementation to be healthy it's not really worth it.
All they mention is meat causes heart disease, and all kinds of other issues which is not true. When you eat meats like red meat along with simple carbs is problematic. So the reason for some of the issues is that most people are eating fast foods which are saturated fats along with simple carbs. The studies aren't good because they're not controlling the variables by separating people who eat fast food from those who eat grass fed beef and healthy veggies.
There is lots of anecdotal evidence that shows the keto diet, and carnivore diet are much better. There needs to be studies, but the anecdotal evidence is very strong. Check out the magic pill, it's another documentary on keto. Only in the last few hundred years these grains and simple carbs became popular, before this we didnt eat wheat, flour, corn, and all this garbage. We also had times of fasting which also shows great health benefits. If your interested in some good research on diet and health check out Dr. Rhonda Patrick. I may have spelled the wrong, but she does lots of studies on longevity and health.