Home / Weak arguments / Exaggeration or attack
"There's no such thing as an ex-vegan."
They claim more than the evidence supports, or attack people instead of discussing what they do.
Why it is weak
Being vegan is an ethical position held up by arguments and repeated choices, not a genetic trait. Any such position can be abandoned. There are ex-abolitionists, ex-feminists and ex-pacifists for the same reason.
The phrase confuses whether an argument is valid with how psychologically stable the people who accepted it are. A position can be more desirable without being quit-proof.
The variant "whoever quit was never really vegan" is the "no true Scotsman" fallacy: it redefines the category after the fact to exclude the counterexample. It also assumes access to someone's inner conviction, which no one has.
How to say it better
Ex-vegans exist, but that says nothing in favor of the position they went back to. Someone ceasing to be an abolitionist doesn't make slavery acceptable.
There are, indeed, people who call themselves vegan while supporting exploitation, almost always because they don't know what the word means. That's different from denying that someone was vegan and changed.