I too will concede the general point. But, they raised 4-H meat birds, and in my opinion, I think we have evolved past using rocks past using rocks to harvest animals.I will concede your point, but I think if we are raising something for the purpose of killing and eating it, we have a certain duty to the creature to take its life humanely. There are many opinions on what constitutes humanely killing a chicken, I will grant that, I just don't see using big rocks on the list.
Nuff said.