I can understand a vegan being ultra fussy if their veganism is a ethical choice.
When almost all commercial foodstuffs contain the products of industrial scale slaughter such a person finds it difficult avoiding meat products when eating out.
Most people simply turn a blind eye to how their meat/dairy/chickens are produced.
If you’re proud of being a carnivore, I suggest you take a visit to your local abattoir on killing day and listen to the distress of the animals as they approach the business end. They give every indication of knowing what’s about to happen. (Try not make mental comparisons to Auschwitz)
The vegan is not being an arse, he’s merely trying to avoid being an unwitting party to what he considers barbaric practices.
(No, I’m not vegan, but I haven’t been keen on meat products since watching the business end of an abattoir. Put me down as an occasional carnivore avoiding the issue).