"If a representative of any species can come to me and explain why thier species should not be killed and eaten by my species, then I will refrain from eating them forever, and I will advise my fellow humans to do the same."
I said that to a vegetarian after an extended argument in which neither of us were getting anywhere. I then stole his sandwich.
I'm a cunt
Anyway, to provide an actually useful answer, I think the reason humans generally accept the mass slaughter of food-animals to be acceptable is very similar to my bastard-response above. We may not admit it, or be able to defend the position, but I think humans generally look down on other species as inferior. If I worked in a slaughterhouse, and one day I was just about to kill a cow when it said "Excuse me, old chap, would mind... you know,
not killing me? Ta." I would of course reconsider immediately.
Wouldnt you?