"And keep in mind that this doesn’t scale very well due to the massive land it requires. Already clearing land for pastures is a large deforester. Trying to even scale to a quarter of beef demand would require using 100% of grassland which would put enormous pressure for further deforestation."
Most deforestation is intended to produce land for crop farming. There is still a lot of agricultural land left that is ideal for grazing, and that cannot be used for growing crops. We may not be able to feed everyone in the world on meat, but we definitely can't do it with plant-based foods alone.
And apart from that issue, there is the matter of protein quality, which is complicated to assess. Most mentions of plant protein are referring to total nitrogen content ("crude protein"), but not all of that comes as amino acids, which is the only form in which nitrogen can be assimilated by the human body.
So mixing and balancing plant protein sources has to be done with a certain amount of skill and care, because if one of the essential amino acids in the mix is deficient, that limits the assimilability of the rest of them.
It's funny: the forum I help moderate has a strong contingent of zero-carb/carnivores, and their experience is the same, only in reverse. They get shamed for not eating plants. I guess the moral is that people will criticize us, no matter what we do.