> As unethical as eating soy from a deforested area.
Not really, though - the GP link says it takes 50 calories of feed to make 1 calorie of Beef, so eating the feed directly would require 50 times less land.
Let me doubt that assessment. That would be true if (1) the 50-to-1 was true (doubt it); (2) what we feed the cattle is human-grade food and (3) 1 calorie of a plant was as nutritious as 1 calorie of meat.