well, of course i do, i didnt comment on that part so my opinion i guess wasnt complete, if they are saying that, perhaps there are certain health issues related to a vegan diet they are focusing on, i'm sure the benefits outweigh the downsides for most people, but yeah.
Also, there is such a thing as b12 deficiency, certain fatty acids aren't easy to get as far as i know, i know things like flaxseed, chia, etc have certain parts of fatty acids, but lack in other parts (i'm not currently read up on it, i just take a capsule every day and not think about it lol)
b12 is made in the body, yes, but it's also made in other things bodies, so when people on an omniverous diet eat them, they get an extra source of b12, otherwise you may take a supplement to help with that
what magazine was this? i have a hard time believing they would say something so, i guess controversial, although they might be willing to since, veganism is somewhat of a niche diet.
The Institute for Proper Nutrition (UK)'s Summer magazine.