Hah, 10 years ago I had a discussion with this guy from school. I've been a veggie all my live, while his friend had become one when she was 13.
He told me that I wasn't a good vegetarian, because I needed to try it before I could refuse it.
So I said: "You have to murder somebody before you can decide not to murder anyone?"
He replied that was different and he'd come up with another example.
He was thinking for 5 minutes, then he gave up.
