Common laws provide certain protections for certain protected classes of people, and are designed to eliminate discrimination for things such as religion, gender, nationality. This is because such things are uncontrollable (race) or shouldn't be controlled by the workplace (religion).
Diet is not such a category.
People making fun of other people can be inconsiderate, but isn't necessarily a violation.
delicious but vegan pastries
They [said] "oh they don't taste as good as the ones with milk and eggs" (but they actually are [delicious] like some [other people have] said)
(I added some words in brackets, based on how I interpreted the statement you said.)
Okay, so let me get this straight: You identify the vegan pastries as delicious. Then other people provided a different view, and you phrase things like as if their comment is wrong.
"Taste is on the tongue of the beholder" is not really a well-known phrase. However, the reality is that "beauty is in the eye of the beholder" is much more true of taste than beauty. Some people dislike certain foods, including the taste of many vegetable products. They are not incorrect. This is not a scenario of correctness/incorrectness. This is taste. Taste is preference, and not an issue of accuracy.
You are being highly dismissive of the point of view that they provide, as if it is a wrong, incorrect point of view. The tastes that you find to be delicious are not necessarily what they find to be tolerable. This does not make them wrong.
when it comes to talk about food where I say my opinion on it, I always receive some kind of passive[...]
(The emphasizing boldness was added to the original text being quoted.)
So the comments that they make, which you find unpleasant, are their responses to comments that you make. "I say my opinion" are your very words. Then, after you spread your opinions, they state their opinions, and you're feeling offended.
In particular, it seems you're objecting to them doing this (spreading their opinions) on repeated occasion. So you're really inviting the criticism, by continuing to discuss views that you know are disagreed with. If you don't like the way that the conversation keeps turning after you provide views that you know they disagree with, then maybe you should just stop provoking them.
I'll even quickly address the examples you provide.
"even plants suffer"
Sure, they don't scream if you tear off one of their limbs. But plants are life. I don't think they suffer too much by ripping an apple off of a tree that will just drop the apple shortly later. But do you think that being uprooted is good for the plant?
"man was made to hunt animals"
Though man may have started out eating vegetables, there are records of early men hunting.
Their comments don't really seem to be wildly inaccurate. Yes, their comments do seem opposed to the vegan point of view. However, they don't seem to be comments that belittle you as an entire person that has other (unrelated) aspects to your life.
(for sure, in the supermarkets nowadays)
Immediately after mentioning their comment (about hunting animals), you waste no time throwing in your own sarcastic slant. You're hardly being successful in this attempt at portraying yourself as the innocent victim.
You're just not enjoying being on an unpopular end of a disagreement. Being on the less popular side can make you feel like you're losing the argument. If you feel like these people won't be swayed to your point of view, then your best bet may be to simply avoid such discussions.
You could still be nice to your co-workers, and label your shared foods so that they can easily avoid experiences that you know they would find unpleasant. (By labeling your pastries as "vegan", they can know to skip over such foods if they find that type of food to be distasteful.)
Understanding An Objection
They do not have a particularly strong case for objecting to other people eating food (like vegan pastries) that the other people find more delicious. If they do appear to be annoyed by such a thing, it is probably because they find that contributions of such foods result in less food that they do appreciate. (If there's too much vegan food, and not enough food with other tastes.)
This "problem" (in their view) can seem particularly annoying to them when vegans eat less overall (which seems to be a common occurrence, perhaps related to the ideas that women seem to frequently eat less than men, and veganism seems to attract more women than men). So not only is there a higher-than-they-desire proportion of vegan food at the start of the event, but the vegan offerings don't even go away over time (like the foods that they do enjoy), because the vegans don't even bother to eat (much of) the stuff that they bring, and so 20 minutes later they are out of food that they see as delicious, and just see a ton of unappetizing vegan offerings.
This can be annoying, particularly if the non-eaters end up hearing people's efforts to try hard to find somebody to give the leftovers away (instead of enjoying it at home). It's not just an undesirable experience of counter-top space being dedicated to food that they need to spend effort to avoid (or, even worse, failing to avoid, and suffering through an unpleasant taste). Even worse than that, it ends up being a problem that just doesn't go away. Instead, it just continues to lingers on throughout much of the day (in comparison). Instead of 3 minutes enjoying a tasty treat (like what is experienced with traditional cookies that people grew up with), the vegan offerings seem to have an undesirable impact for 20+ minutes.
If you were to bring a mix of vegan offerings and non-vegan offerings, with such a split that the vegan offerings tend to be fully eaten, such a move is more likely to be seen as a friendly gesture. And why are you even having such snacks/meals, except to be a social event that presumably is intended to be friendly?
Note that I'm not saying that you have any obligation to do this. I don't know enough about your situations (structures of your social dynamics/events) to identify what you ought to feel obligated to do. Isolation may be preferable if you're planning to leave anyway, and don't wish to invest in such niceness. What I am saying is that this approach could be a win/win opportunity which you may wish to consider if your wish is to have people be happier. You'd win by having happier co-workers that are less likely to be antagonized into discussing a topic which is actively annoying them (and thereby creating discussion which has actively annoyed you). They win by enjoying the food that is offered. Granted, this sounds like more of a win for them, but that's better than you losing by feeling terribly agonized, like you were when you wrote the question. Being nice is more likely to result in you experiencing the win of one of them being compassionate and including a mixed offering themselves, remembering your position of choosing to avoid their foods just as they choose to avoid yours. Whether you find such benefit (or potential benefit) to be worth your costs/effort is a decision you'll need to make yourself. I think you should do this, but that is because I think people should humbly strive to make other people happy when they have a chance to do so. I am not saying there is any cause for you to feel any specific obligation to take this good course in life.
Edit: Added this next section:
If you don't want to positively invest in what other people will be interested in, fine. If you don't have a thick skin, then simply do not engage in discussions that you expect will not turn out desirably. People with at least some interest in being respectful may get less enjoyment out of making anti-vegan comments if they learn that it repeatedly turns into a rebuttal that feels less amusing, like hearing "Let's talk about something else. Please."
Still, labeling your foods (as an advertisement for proponents, and a warning for the detractors) is considerate. Such politeness is still recommendable.