Never shamed a vegan, and I was one myself for 5 years. I think people get a negative impression of vegans because vegans so commonly share their reasoning, even zealously or evangelically so, unsolicited.
It gets annoying. And I felt that so much (in others) while I was a vegan that I stopped explaining why and just said "personal choice" when asked.
If someone wants the whole story, they'll ask for it. We don't need the morality, the economics, and the all-to-often (admit it) holier-than-thou diatribe vegans are so wont to subject others to.
In my experience, the reactions depend a lot on the people you talk to and well, what you look like.
Like, I've got a tiny lady colleague who's vegan and she's never been in a conflict from being vegan.
Meanwhile, me as a big dude, I will get various males who take it as a personal affront:
those who are just insecure about their own food choice,
those who take every interaction with other males as a competition for who's better (me telling them I'm doing it for ethical reasons means I'm saying their ethics are bad),
those who are stuck in their old ways (women can eat salads, not men though),
and last but definitely not fucking least, (ex-)military dudes who are personally disappointed that, despite me having the physique of their military buddies, I have different values.
This is especially also amplified on the countryside, where not only progressive ideas take longer to arrive, you've also got farmers with skin in the game.
In my hometown, there's a pig farmer. Holy fuck, for that guy, my mere existence was a statement that his entire livelihood is immoral.