I’ve dealt with lots of vegetarians and a few vegans - plus all sorts of other dietary restrictions. I don’t hate any of the people, but there are a few behaviors I dislike:
I dislike anyone making their food choices my problem - with an attitude. I can cook vegan, please tell me before you walk into the door. And I’d appreciate it if you informed me with an “I’m vegan, can you make a salad or something or should I just bring my own food/eat before I get there.” That’s way better than sitting down to table and annoucing “I can’t eat ANYTHING here, I’m vegan.”
I dislike anyone believing their food choices trump my own and my other guests. Yes, I’ve cooked a tofu/bean and veggie pasta salad as a secondary main dish for you, if meat on the table for everyone else offends you, please don’t bother to come - we are not a vegetarian household.
I dislike anyone making comments about what goes into my (or anyone elses) mouth during dinner - I’m equally offended by “that poor cow, don’t you know how much worse meat is for the environment” as I am by “your vegetarian! You sickly pale thing, cows are meant to eat - here have a steak!”
I dislike anyone making comments about how superior their food choices (or lifestyle) is - its judgemental and inappropriate. Few of us lead a perfect life - there is almost always someone leaving less of a footprint than you are (or I am), and there are a lot of variables that impact how you are going to choose to live your life. Do animals suffer by becoming my food? - sure - but there is a hell of a lot of human suffering going on, some I am indirectly participating in just as I participate in the butchering of a chicken. And its almost always hypocritical - I know vegetarians who go on endlessly about the healthiness of their diet and smoke (what is with that anyway) and the vegans (we don’t want to hurt the cute animals and we want to protect the environment) who drove the his and hers matching SUVs (but we need them for the sixty mile commute to get to our jobs from the mountains!)
Now, as I said, I’ve known lots of people with food restrictions - what I do like:
“Just in case you forgot we are vegan, we brought our own veggie burgers.” Then they unobtrusively without mentioning why put down a layer of foil over the grill to cook on - or quietly ask whoever is cooking to do so.
“Thanks for the dinner invite, but I’m a pain in the backend to cook for - I have celiac so I can’t have gluten.” (Responded to with “oh, that isn’t a problem - I can cook around that.”)
“Would you mind if I chose the restaurant? - I’m vegan and there are a few restaurants that are much better for me.”
“I’m going to turn down the dinner invite - we keep kosher - right down to the kitchen - and don’t eat out. But if you don’t mind, we’d love to stop by after dinner to visit.”
(I spent some time this Spring on a business trip - and three of us went out to dinner - I’m gluten intolerant, one guy is Muslim and keeps those dietary restrictions (Halal?), the third was vegetarian - we end up eating in the worst possible greasy spoon diner for each of us - and while we laughed about it, we made due and none of us complained.)