Regardless of a hundred different ethical and meta-ethical theories that people espouse, what everyone actually reacts to with outrage is plausibly-generalised threat perception.
If someone’s actions are directly threatening you, you’ll feel anger and/or fear.
If someone’s actions don’t affect you or yours, but :stuff like that: being commonplace definitely would, then you will feel outrage.
If I kill people and take their stuff, you’ll be very upset: you’re a people, and you like stuff - and if we let the general case happen, the specifics could come bite you in the ass soon enough.
If I kill and eat animals, most people don’t consider it plausibly worrying that they or little Timmy will be next. We have great big enormous taboos against eating people, so that slope just don’t slip - and as a result they just don’t have a problem with it.
(If I go and torment animals for lulz, then that’s a very different case; people who are cruel to animals are often even worse to people, after all - and so people see that as monstrous. And again, if you want to manufacture consent for some atrociy, the easiest way is to reclassify the victims as qualitatively different. Oh good lord no, we’re not killing people and taking their stuff, that would be awful. Nonono, we’re killing :group: and taking their stuff, totally different proposition…)
So when vegans are horrified at people killing and eating (or breeding and milking, or whatever) animals, and go to great lengths to try and elicit that same outrage, there’s a disconnect and dissonance going on. The non-vegans don’t have the emotional trigger of perceived threat, so to have them keep trying regardless is seen as pearl-clutching and sleeve-tugging, like making up a sad story and loudly demanding that everyone weep about it on the spot. It’s uniquely annoying. And when you combine that with (perceived) moral superiority and a hypercritical attitude, it comes across as something like a Karen with BPD. It’s calling red on someone else’s scene; everyone is supposed to cater to the vegan’s emotional distress when there’s no corresponding emotion in themselves, and honestly that just provokes people to schoolyard bullying.
That’s at the core of it, I think. There’s a bunch of other annoyances around it, but I think they’re mostly after the fact.
Honestly if you want to make people feel that general existential threat, frame it in terms of ecological damage. Animal agriculture is horribly unsustainable and causes huge enviromnental problems, not least of which are are a truly gigantic carbon footprint. Pushing that angle would actually stand a chance of being effective, tbh. But annoyingly (from the outside), it seems that the most vocal vegans don’t want people to be outraged on that basis, they want them to be outraged for the poor little lambikins, and will settle for no less. I can see their point, and I can be a stubborn bastard myself about not settling, but jesus fuck it’s annoying.
Not a vegan, though I’ve been mostly-veggie for the last couple of years for health reasons. It’s interesting how it shapes your perceptions; eating meat doesn’t seem wrong to me, but it has started seeming weirdly excessive and uncreative.