Well said. Some of these people also take some kind of sick pleasure in viewing/"exposing"/sharing disturbing videos and media involving animals being abused, butchered, dissected, that sort of thing. For people who supposedly stand against this sort of thing, some sure do have a sick fascination with it.
I had a schoolmate who went vegan and proclaimed the disgustingness of the meat industry, yet, she would spend her spare time watching YouTube videos of animals being slaughtered, while eating vegan "beef" jerky.
It all goes back to my theory about that type of diet missing nutrients that are essential for proper brain function. Loose screws.
A lot of this makes me think of people I've known who'd recently quit smoking, who are rude and obnoxious towards people who are still smoking, in an attempt to get others to quit smoking. They'll show them pictures of diseased lungs and spout statistics like they're getting paid to do it. Yes, some can be obnoxious i their zeal and misguided enthusiasm, but in both cases they probably mean well. But there are plenty of others, and I speak of both smokers and vegans, who go quietly about enjoying their new-found freedom, or passion, without bothering anyone. You just don't notice them because they don't make themselves noticeable. Those that are jerks would be jerks whether they were vegans or non-smokers or any other category you'd care to put them in.