Judging any group by its worst members isn't the most charitable regardless of the group. You end up not really making an argument outside of "I found a ridiculous person in this group" which like, yeah, true. But when you imply that they're somehow representative or to be taken seriously you end up just exposing your prejudices and/or ignorance. Dogpiling a person who thinks you can photosynthesize b12 is fine -- they're nuts. But if that person sours your opinion of V's then you clearly already had issues with them.

Veganism and vegetarianism aren't synonymous with healthy, they don't even try to be. It's actually a point of annoyance among V's that "vegetarian" options at restaurants try to be "light" and healthy when you really just want a basket of fries dipped in vegan mayo. Same with the aversion to processed foods, it's nothing to do with V's at all -- that's the "whole foods" movement thing. Some V's care about the environment, some V's care about whole foods, some V's care about animal suffering. The former two probably wouldn't eat an Impossible Burger, the latter might.