The author of the article you mentioned (Alex Howe) is a good example for what I insinuated: He takes issue with Korsgaard’s argument (and, it seems, Kantian ethics more generally), but in his PhD thesis argues for granting “basic citizenship rights” to domestic animals (including farm animals), which is arguably a far more radical position than veganism, which merely posits that it is immoral to exploit (or be cruel towards) animals (e.g. as a food resource). Either way, if you have an issue with Kantian ethics and how they are applied to animal rights, I suggest you take it up with a Kantian (which I am not). And, even if I am repeating myself, none of this has any direct relevance to my earlier point, which is that many moral philosophers from many different schools of thought (including, but by no means limited to, Kantian ethics) have arrived at conclusions which are at least similar to the basic vegan stance, i.e. that unnecessarily causing harm to (sentient) animals, e.g. by exploiting them as food, is immoral.

I didn’t say anything about Kant himself (Kant also thought that non-human animals were basically just “things” without rationality or self-consciousness, which is however in direct conflict with the current scientific consensus. Kant still argued in favour of treating animals “humanely”, just not for their own sake). Anyway, some well-known and well-respected contemporary philosophers who argue(d) from a Kantian perspective in favour of animal rights include e.g. Christine Korsgaard or Tom Regan, and many lesser known philosophers (see e.g. here for a recent example). I also see no indication that these types of arguments as a whole are supposedly “thoroughly rebutted” (not that serious philosophy really works like that anyway). Some other philosophers disagree with some of their arguments, of course (this is normal in philosophy), and many don’t subscribe to Kantianism in the first place, but afaik most of them tend to take issue with how Kantian ethics is applied (or that it is applied) moreso than that they’re trying to defend animal exploitation as such. Either way, none of that changes the fact that ethicists have been using Kantian ethics (among many other meta-ethical frameworks, as I said before) to argue in favour of animal rights, and that there aren’t really many arguments in defense of killing animals for food (in particular in the context of factory farming) that find widespread support (among moral philosophers, that is).

I didn’t think the had an official organized statement

There sort of is. The term “vegan” was coined by some members of the Vegetarian Society of the UK in the 1940s (at the time veganism and vegan diet were mostly referred to by terms such as “strict vegetarianism” or “no animal food” etc.), who shortly after founded the Vegan Society [of the UK]. The latter has an “official” definition of veganism:

“Veganism is a philosophy and way of living which seeks to exclude—as far as is possible and practicable—all forms of exploitation of, and cruelty to, animals for food, clothing or any other purpose; and by extension, promotes the development and use of animal-free alternatives for the benefit of animals, humans and the environment. In dietary terms it denotes the practice of dispensing with all products derived wholly or partly from animals.”

Of course individual vegans may have slightly different definitions, and may interpret them differently, but as a whole this seems to be a fairly accurate definition for many vegans (although there are some exceptions, e.g. people who adopt plant-based diets for (percieved or actual) health benefits, or religious reasons, sometimes (but not always) also refer to themselves as “vegans”).

As to the “literally right” part (I assume the OP was referring to veganism in general, not the specific issue of the thread), it mostly boils down to whether or not we think the statement “it is (morally) wrong to unnecessarily cause harm to animals” is correct. Since most people (with perhaps the exception of some with rare medical conditions) can survive just fine on a diet free of animal products (same goes for clothing etc.), we can conclude that it is at least unnecessary to use animal products. Thus, if we agree with the rest of the statement (i.e. that exploiting animals for their meat or other products causes them harm) we should also agree with veganism as an ethical stance. Naturally this could be discussed in much more detail and with many caveats, but for me this is more or less the core of the argument. And as it turns out, a lot of moral philosophers from different meta-ethical schools (such as utilitarianism, Kantian ethics or virtue ethics) seem to agree at the very least that the arguments in favour of veganism are much stronger than those in defense of eating meat (and particularly those in defense of factory farming). Some further reading for those interested:

• https://en.wikipedia.org/wiki/Ethics_of_eating_meat
• https://en.wikipedia.org/wiki/Veganism#Philosophy
• https://plato.stanford.edu/entries/vegetarianism/

There seems to be a bit of a difference, even though both involve asking questions. To quote wiktionary:

sealioning (uncountable)
A type of trolling or harassment that consists of pursuing people with relentless requests for evidence, often tangential or previously addressed, while maintaining a pretense of civility and sincerity (“I’m just trying to have a debate”), and feigning ignorance of the subject matter, in order to wear down an opponent and incite angry responses that will discredit them.

Apparently coined by this webcomic:

JAQ off (third-person singular simple present JAQs off, present participle JAQing off, simple past and past participle JAQed off) (slang, derogatory) To ask loaded questions inviting someone to justify their views or behaviours, in an attempt to make tangential claims of little verisimilitude appear acceptable.

So the way I understand it, “JAQing off” is when you’re trying to guide your audience towards a certain conclusion without stating it outright (e.g. “Are the official numbers of holocaust victims really as solid as people claim? Are there alternative historical interpretations? I’m just asking questions here, not implying anything folks.” when you think just saying “The holocaust didn’t happen!” might make it too obvious you’re a Nazi), while sealioning is more about annoying the other party and trying to make them look bad/unreasonable and yourself polite and reasonable in comparison (e.g. “I’m just curious, is there any actual evidence that fascists are inherently bad people, as you claim? As a person with no opinion on the matter, I would just like to have an honest and open debate on this subject.” so when people reply with something like “Fuck off, fascist!” you can say “Wow, so much for the tolerant left.”). Both tactics are frequently applied by online trolls, especially of the far right, but they have somewhat different goals.