That's not really the point. The point is only that the suggestion that there wouldn't be enough land to feed people if they stopped eating meat is patently false.
That is completely the point. Currently livestock graze over huge amounts of land in the UK that is at this time unsuitable for growing crops on. Mostly vast areas of moorland, fells, peat bogs etc.
They do this alongside groundnesting birds, insects, hares, deer, foxes, rabbits, snakes, mice, voles, geese, badgers, moles, frogs, toads, butterflies, moths, beetles, stoats, crayfish etc.
If in La la vegan land where all the land currently grazed by livestock is given over to vegetable growing most of this land would need to be ploughed, drained, sprayed, fertilised with artificial fertilisers, and heavily pest controlled. Trees and hedges would need to be felled to allow tractor machinery to pass systematically.
What happens to all of the animals that were happily coexisting alongside livestock previously? Do they go to the sanctuaries too?
How long do you think the soil will continue to be productive without the nutrients from animal manure and urine going back into it?