This implies that the land used to grow cow feed couldn't be used to instead grow human-consumable crops or left fallow as a carbon sink. I'm not aware of any studies showing that.
You make a strong argument. I think this is a case where we'll find the global optimum somewhere in the middle.
Deforesting the amazon to grow corn for cows is something I'm sure we can all agree is bad.
Should we use livestock to eat cover crops and waste products like corn husks and cobs? This way we reuse waste and produce high quality protein to supplement our diets.
Should we graze cattle on natural grasslands like the great plains? Especially in rotation with human foods, like the cover crops mentioned before?
I'm pretty sure that feedlot studies say that the usual situation in the US is that 1/2 of beef calories come from a 10:1 ratio of human edible calories.
So sure, go for 100%-grass-and-not-human-edible-food-fed beef, but that's not the current system.
Lets not forget the transportation of fresh meat is not negligible, the cooling and the fuel costs will add greatly to carbon emissions. Preserved foods and not relying on luxuries such as refrigeration would go a long way to sustainability and heath.
Transportation and cooling of meat in particular is nothing compared to the land area of North America and South America combined that we devote to growing crops to feed livestock.
Is it negligible that transportation of fresh meat, its cooling or freezing are not at all factors in carbon production? I would like to see how its calculated.