All the studies sited are at least 14 years old, one from 1968. They thought black people were inferior to whites then, I wouldn't trust a lot of things they believed in.
The studies may have been funded by meat/dairy/egg companies, probably were. Results like these often come from meat industry-funded studies.
In a lot of the studies sited, fish was the food that did good.
A lot of excerpts were written in a way so that people that don't know much about human biology could understand it. These were then taken literally to prove a point.
A lot of the vitamins that come from animal sources cited do come from animals, however as humans are animals we make our own so we don't need to eat other animals to get them. Other vitamins are more abundant in plants.
As all the studies used to prove the point are only tiny little snippets, there would information missing.
This is one article. So the odd article that says eating meat is good for you proves that all the others are wrong? Righteo.
Anyway, we know that in this day and age it's completely possible to live healthily as a vegetarian. Even if it were less healthy (which it isn't), we would still do it because we care about the animals.