It’s a strange phenomenon.
When I was vegetarian as a teenager, my mother would do things like secretly cook my fake bacon in bacon fat and then reveal the trick afterwards - “oh that tasted better than usually didn’t it?” The TTI facility I was at for a bit would only provide me with just plates of unseasoned canned vegetables, and then crow about how I didn’t care that much about being veg because I wouldn’t eat just a straight bowl of peas.
I think some of it is a weird discomfort/projection thing, because many meat eaters haven’t really seriously engaged with the ethics of eating meat and the existence of other people who have can be seen as a threat. Again - not all people who eat meat - but I think in a world where we are very abstracted from that process of killing the animal the existence of vegans/vegetarians and their food forces some folks to confront their own cognitive dissonance on the matter.
100% it is artificial and socially constructed. I don’t think Adam’s Sexual Politics of Meat has it all right but it has some interesting ideas about cultural messages about meat and masculinity and got me started thinking about it. (It was written for a Daly class, and Daly is the reason there’s a strain of radical feminism that things womyn are magical spirit beings that are tainted by being in any form of contact with an XY chromosome. There’s a reason Limbaugh attacked Dworkin and not Daly and Raymond cough)