I read your dialogue with the vegetarian and there is a rebuttal on your part that was not mentioned. The israelites are human and God commanded them to eat the lamb at Passover and that nothing of it was to be left until morning and if any was, it was to be burned.
Having had a number of discussions with vegetarians, I'm not certain which one you are referring to, but it is true that none of my replies are exhaustive answers. There are numerous ways to show that killing animals for food is not against God's teachings. As pointed out in "Did Jesus Eat Meat?" a person could not be a faithful Israelite and a vegetarian.