The last paragraph is the most important really:
But that’s not to say that in today’s modern world you cannot survive without meat. The millions of vegans and vegetarians are testament to that. Today we have lots of food options available, at least in the developed Western countries. As people are becoming more health conscious, we gain more understanding of the role that high fiber diets have in reducing disease risk, and the concerns we have over animal welfare in farming, more and more people are turning to a vegetarian or vegan diet. As a result of public demand more vegan food, fortified with those essential vitamins, are appearing on supermarket shelves and restaurants are popping up all over the place. I think that’s great. Personally I love vegetarian food and I’m not a big meat eater (more on that later). But I am also passionate about science and factual information, and trying to argue that humans are biologically herbivores and meat ‘rots in our bodies’ makes vegans look more like religious zealots who will say anything to gain followers, even if it is completely bogus.
A lot more people are physically capable of being vegan than are currently so. It is annoying and hostile when militant vegans insist that only very tiny numbers of people can't manage without meat or dairy, and that people with restrictions should have to follow very narrow plans in order to still be vegan (to give an example I've seen a few times online, vegan and low FODMAP and an allergy to another important vegan protein source) but if maybe 60% of the population ate a plant based diet or near as dammit that would make a big difference.
I think it's more helpful and conciliatory to see it as a cultural shift rather than pathologising all vegans. Other cultures might think we are weird for not eating certain animals, and/or for eating dairy products at all.
I suspect that for some groups of teenagers today veganism or trying to be, must be similar to the norm of non-animal tested products among my year at secondary school, to them it's just obviously the done thing.