First, I am not a big fan of having the top-level posts consist of nothing but a link.
Second, the article takes "the intellectual case against meat-eating is pretty air-tight" as its premise. That premise is not even wrong as it confuses values and logic (aka rationality).
Full disclosure: I am a carnivore.
I'm assuming that the LessWrongers interested in 'should I be a vegan?' are at least somewhat inclined toward effective altruism, uilitarianism, compassion, or what-have-you. I'm not claiming a purely selfish agent should be a vegan. I'm also not saying that the case is purely intellectual (in the sense of having nothing to do with our preferences or emotions); I'm just saying that the intellectual component is correctly reasoned. You can evaluate it as a hypothetical imperative without asking whether the antecedent holds.
I'm currently unconvinced either way on this matter. However, enough arguments have been raised that I think this is worth the time of every reader to think a good deal about.
http://nothingismere.com/2014/11/12/inhuman-altruism-inferential-gap-or-motivational-gap/