I ended up in a conversation with some Jehovah's Witnesses a few years ago because I couldn't escape without being really rude so I asked them if they were vegetarian. They said they weren't so I suggested they look at Genesis 1.28. They came back with Noah who asked god for permission to kill an animal after the flood. I pointed out that this rather indicated that you needed direct permission to eat meat and hit them with Isiah. They countered with Leviticus and I pointed out that if you had to back up your view with Leviticus you had already lost and that in any case I had given them two quotes that you should be veggie and they had given me two that you didn't have to be so it didn't fill me with confidence in the book they all came from. A working knowledge of Tom Paine's Age of Reason is handy as well!