It's because the grandparent comment has misconceptions about nutrition, including that animal products are necessary for a healthful diet and how much protein is required for a healthful diet.
The first misconception is contradicted by extensive analysis by health organizations such as [Academy of Nutrition and Dietetics][1]. Healthful vegan diets are no less healthful than healthful non-vegan diets.
The second misconception is about how much protein is needed in a healthful diet. Many people wildly overestimate how much protein a person needs, especially when strength training. It is not difficult to get sufficient protein within a given calorie budget while on a vegan diet, even without using protein supplements. For instance, tofu and seitan have protein to calorie ratios similar to meat, with seitan often having a higher protein to calorie ratio than most meats.
Go and have a look at the amino acid profiles of seitan and tofu and also their bioavailability in comparison to meat and vegetarian protein sources. And you can talk all you want about people overestimating protein macro but 1 to 2 grams per lb of bodyweight has consistently shown to be optimal. You’ll be hard pressed to find any high performing athlete who isn’t aiming for that outside of endurance sports.
At the end of the day in my experience, a vegan diet is both a lot more hard work and less healthy than a non vegan one. Saying that a vegan diet isn’t any less healthy than a meat eating or vegetarian one is an absolute joke, especially considering there are no vegan foods containing vitamin B12 outside of yeast flakes and artificial supplements.
Amino acids - it's suboptimal to eat only one source of protein. I suppose more so on for a vegan. Just as well no one does that. Of they do you're no longer attributing "poor amino acid profiles" to veganism as you are to the person responsible for terrible diet.
B12 - Animal products come from animals filled to the brim with B12 supplements, of which a huge majority of global B12 supplements go towards livestock. Also along with over lovely concoctions of antibiotics and drugs.
There's nothing wrong with cutting out the middle-man! Not least when so many flesh eaters are also deficient in B12 themselves. In need of taking the same B-complex as vegans.
The first misconception is contradicted by extensive analysis by health organizations such as [Academy of Nutrition and Dietetics][1]. Healthful vegan diets are no less healthful than healthful non-vegan diets.
The second misconception is about how much protein is needed in a healthful diet. Many people wildly overestimate how much protein a person needs, especially when strength training. It is not difficult to get sufficient protein within a given calorie budget while on a vegan diet, even without using protein supplements. For instance, tofu and seitan have protein to calorie ratios similar to meat, with seitan often having a higher protein to calorie ratio than most meats.
[1]: https://pubmed.ncbi.nlm.nih.gov/27886704/