i'm a little late getting in on this topic, but i'd like to share what i heard once. i had a biology teacher who was also an avid outdoorsman and he was off on a rant one day in class talking about hunting and eating wild game. a girl in the class then started a debate with him on the ethics of "killing innocent animals", and asking why it was necessary to shoot animals when you could buy food at the grocery store.
the debate went on for a few minutes until she admitted that she was a vegetarian. then the bio teacher asked "do you know the difference between eating animals and plants?" she told him "no", and he said "plants cant scream when you kill them." this was back in college, so she voluntarily left class and didn't return.
i thought it was a great comment at the time and i still talk about it with a friend of mine who was in the class. the teacher is a very respectful and responsible hunter, he just made the comment to get under her skin... and it worked!