Earlier quoted context omitted.
Obviously yes for most people, since vegans are a tiny minority. Bit of a high horse you're on there.
I think most people who are in this predicament consciously choose not to think about it in order to avoid the cognitive dissonance. Destroying your philosophical model of reality and remaking it is not exactly a pleasant process. Something you find out when you go vegetarian or vegan is that if that gets brought up, which usually happens in the context of rejecting an offer of food or being questioned about why your…
I don't think it's a cognitive dissonance thing, at least where I've seen that picture. I think it's an us/them thing. Specifically, the kind where one group gets the idea that another is out to get them. (That "militant vegetarian" you mention is someone I have heard about my whole life yet never met.) If they don't have a lot of vegetarian friends, you may be their first chance to have a conversation about it, and that's probably the only one they rehearsed.
It may not be as crystallized as other areas, yet, but I think this is also one more field for cultural proxy wars, as we all get drafted into us/them camps. Again, at the individual level, you might notice the person doing the attacking always thinks they're defending. Complicated big picture stuff at play.