First a disclaimer: I do not have anything personal against vegans who aren't obnoxious, belligerent, bullying assholes about their lifestyle choice. There ARE vegans are totally chill, reasonable, rational, respectful human beings. It just so happens that there are a LOT of vegans out there, who have absolutely earned their negative reputation as snotty, confrontational, entitled, self-righteous assholes. The following is addressed to THEM.
A few reasons why, even though not ALL vegans act/think this way, that veganism at large is a cult:
1. They truly believe that their dietary choice makes them better people, in fact, superior people, to those who choose to use animal products, especially those who eat meat.
IE They believe they have the One and Only Truth, and knowing it makes them the best people on the planet.
2. They genuinely believe that it is impossible to love animals, or care about Nature/The Planet, if you eat meat. They also believe that eating meat essentially makes you an ignorant, even bad/evil person.
IE People who do not follow their doctrines are "sinners" and "heathens", who either need to be condemned, or "saved".
3. They genuinely believe that veganism is THE only way to go, and THE only thing that is going to save the world. They believe this so much, that they constantly proselytize it, and actively desire to keep on spreading veganism until everyone on earth is vegan.
IE It isn't merely a dietary or lifestyle choice as far as they're concerned, they believe it is "The Way", and they wish to spring this "One and Only Truth" to the masses, to "save" us from our own ignorance and evil.
Even one of those things, let alone all three, are textbook examples of a cult. Many vegans literally worship at the altar of veganism, and consider everyone who is not part of their elite group, lesser beings. None of this is hyperbole or fabrication, because I've based it 100% off of vegan propaganda and sentiments I've seen expressed across various internet and social media forms.
Word to the wise: Your dietary or lifestyle choices do not make you "superior" to anyone. And while farming practices do absolutely need to change/improve, no, you don't need to spread your "superior" ways to anyone else. And yes, people can care VERY much about the planet, in fact likely far more than you claim to, while also choosing to eat meat. Keep your bullshit to yourself, and respect those who don't choose to live that way. Otherwise, you don't deserve an ounce of respect yourselves.