Off-topic, but speaking as a non-veggie, I somewhat disagree on the idea that vegetarianism is an arbitrary distinction.

Of course from the perspective of killing things, it absolutely is - but from the standpoint of causing the least pain possible, then vegetarianism would be more ethical (and veganism moreso) as to my awareness plants can’t feel pain beyond automatic trauma responses (I.e. releasing pheromones).

Until we evolve to photosynthesise and pull nutrients from the ground (timeline never), I would argue that it is always more ethical to kill something incapable of pain than to kill something capable of it.

As to why you got so much push back, my opinion is that your argument sounds an awful lot like the “conservative” argument of if it’s not perfect, it’s not worth doing at all. An argument that a lot of people get frustrated by at the best of times.

Albeit, if you want to point out the arbitrary nature of a diet, I might point you towards Pescetarianism, basically a veggie who eats seafood. I find the idea of an ethical boundary based on habitat to be completely arbitrary.