I feel like you’re doing the thing you premptively accused me of wanting to do.

I disagree. You're bringing up those same other issues "in the context of land use" and I'm trying to respond as best I can while sticking to land use.

You’ve put forward an arbitrary unsourced number asserting that 2/3 of the land used for animal agriculture is otherwise useless for food production

Are you saying you contest the 2/3 number straight out? Because your previous reply seemed to be trying to gather ammo to object to it with supplemental data.

with the implication that we would need to use more high quality land to meet human food needs

I actually didn't make that implication. As "it's ok to keep eating meat" is the defacto winner, I'm simply pointing out that anti-meat advocacy has not resolved the marginal land issue with their land use objections.

That number is undiscussable until you can actually demonstrate to me how you’re arriving at it

Alright. So is your position that there is no such thing as marginal use land, or that there exist no cows on it? If we "undiscuss" that number for a moment, are you willing to concede the only point I made - that livestock on marginal use land is perfectly fine from an environmental point of view?

We can’t have a discussion if you’re asking me to work out the specifics of your claim and then disprove them, you have to actually make a specific claim.

My claim is that the vegan argument on marginal land hasn't defended their claim. I have argued that claim, and you're harping on a number you both believe enough to try to argue around and disbelieve enough to pretend it's impossible to discuss marginal land use without me somehow proving the number is exactly correct.

Does the 2/3 number matter to you, or doesn't it? Do you believe it, or don't you? If the former, maybe we can have a discussion on exactly how we can determine how much livestock is on marginal land. If the latter, perhaps we can focus on whether livestock on marginal land is horrible for the environment or not.

Getting into the weeds on the details of soy and hashing over the whole by/co product

I really didn't. You made the claim that soy represents secondary land use, one I took seriously enough to reply while pointing out how the reply can lead to tangents, so we can stick to the argument. ANOTHER person, in response to me (and maybe you) provided far more tangential, but effective, an argument against you, but I am not that person.

So please, make that claim

Which claim are you asking me to make now? Can we finish the claim "vegans haven't proven that livestock on marginal land is terrible for the environment" first?

I think the whole issue is that this is more complex than any discrete set of metrics because so many industries are interconnected. in a world without any animal agriculture, how much corn and soy would we raise? it is just unknowable.