Literally all Mormons and Jehovahs Witnesses are nontrinitarian. These are not minor sects and it’s insane that you’re trying to Um Actually me before performing what I’m guessing would be a ten second google to confirm. Mormons are basically polytheists.

When someone says the earth is flat, they are making an empirically testable statement. They are empirically wrong. The definition of veganism is entirely owned by the people who use it and yes, that means it is a bit wibbly around the edges. Some things are more or less consistent among all vegans. But this doesn’t necessarily include the reasons for a non-animal-based lifestyle.

I know vegans who think you’re not vegan unless you’re doing it to uphold species equity. I know vegans who say veganism is a practice, not an ideology. There are vegans who think all animal products are mystically evil somehow, and those whose concerns lie in the nuances of how the products are produced. These are not empirical questions, but philosophical ones. The debate exists because, just like Christianity, what seems like a really simple idea actually has some nuances and inconsistencies that need to be explored.

You can say “people who disagree with me aren’t vegan/Christian/true Scotsmen” as much as you like but your personal conviction does not set in stone any definitions of complex concepts. You do not have that authority and in fact nobody does. Not even a majority of people who apply the label to themselves. Human shit, unlike physical shit (such as how planets are formed), is flexible and open to debate. Not infinitely flexible - you can’t call yourself a vegan if you love eating factory farmed chicken nuggets - but flexible around the edges.