This article is problematic on a number of levels.
It appears to misunderstand protein or perpetuates the myth that humans struggle to get enough. There is no need to obtain protein from animal products and in fact animal based proteins are a primary source of cancer. Additionally, Vegans including those that do not wholly or mainly practice a plant-based whole food diet, have higher levels of protein than meat eaters. Protein deficiency is a 'bogeyman' - you've never had it and you've never heard of anyone who's suffered with it.
Speaking of deficiency, low levels of B12 are more prevalent in meat eaters across America than vegans.
There is absolutely no requirement to eat animal-derived products to maintain good health. A plant-based whole food diet has been shown to be optimal for health, please see the China Study. It is also stated as adequate for all stages of life, by the World Health Organisation and the American Association of Dietetics, including childhood, old age, and pregnancy.
Meat, eggs and dairy on the other hand can be classified as high-risk foods that aside from their cancer and heightened cholesterol causing effects are a source of pathogens, and in many cases such as with chicken flesh, sodium!
Fish flesh is no exception. Fish consumption is the leading source of mercury, dioxins, neurotoxins, DDT, putrecine, AGEs, PCBs, PBDEs, and prescription drugs. Among the undesirable effects these contaminants can have on us are lowered intelligence; lower sperm counts; more symptoms of depression, anxiety, and stress; and early puberty.
While meat alternatives from Beyond Meat and Impossible aren't as healthy as vegetables, fruit, beans and nuts, they are 'clean'. It has also been demonstrated that humans are far better off with plant proteins than with animal proteins. Animal proteins promote cancer and plant proteins not only do not, but in some cases reverse it. Again, see China Study.