Well cults aren't mainstream, so that perfectly why these particular vegans are displaying cult-like behaviours. As I said, I wouldn't use the word cult, I don't want the word to be diluted to the point anyone with extreme ideas is part of a cult, but I can see parallels there.
So any group that calls out people that don't agree with them (attacking and shaming apostates) is cult-like?
That would make any Pro-Life group cult-like, global warming advocates cult-like, Christianity cult-like, etc.. If you're going to use broad generalizations to define a cult, inevitably everything begins to seem cult like and you can draw parallels. It's nonsense.
I suggest you read my conversation in this thread with @sanctified, particularly what defines a cult. After reading that definition, you'd understand that any military, or North Korea, has more parallels with a cult than what is known about this group.