Why is it relevant whether one can put a finger on the difference? The claim was that people use their economic distance from meat production to protect themselves from the negative feelings that would be created if they had to do it themselves, especially in the manner of factory farming.

Anyway my theory for the distinction is 1) the scale of suffering is obviously far far greater than family-scale slaughter and 2) the way in which we do factory farming reflects poorly on us as a species.

If people had to see their livestock suffer, they would make a different calculation of how much meat to eat and how to handle that animal while it’s alive. As someone else mentioned, this isn’t some crazy avant garde hypothesis: this is exactly why mass meat producers don’t want people filming their operations.

The prior argument that “people always killed animals!” is irrelevant. They certainly did not kill animals the way we do today and again, this is evidenced in the belief systems that emerged during times where people couldn’t afford to be hundreds of miles removed from the production of their food.