My one rule on this topic is never getting into a gishgallop. Vegan advocates love to play the roulette of swapping topics every time they lose ground on one, until they manage to win the argument having lost every piece of it by just tiring the other side out. You pick one of those topics, and I will field that topic only with you. It might surprise you, I will agree with you on some of them (like saving the Amazon).
But if you make me choose, I will choose land use because it's a slam-dunk. 2/3 of agriculture uses marginal land that cannot (and I believe should not) be made arable. If resources were spent changing that instead of vegans fighting with farmers, that number could approach 100%. There's important asterisks about that (both crops and livestock become more environmentally friendly if done close to each other due to their symbiotic relationship) that need to be kept up. But reducing livestock population directly WRT marginal land is wasteful.