"Tell me why you hunt animals instead of people."
"Well, gee, Bella... I wonder why anyone would ever consider not murdering for their daily meal." As soon as he said it Edward realized that making a poetry reference was probably pointless. If she understood poetry she'd probably be able to understand the value of human life. He decided a different approach, "Why don't you eat people?"
In the pause that followed Edward came to the disturbing realization that she was thinking over the question and not coming up with an answer.
"Forget I asked that." Edward nearly shouted. He took a moment to compose himself and continued, more calmly but his voice still quick and agitated, "Seriously. Forget it. Never ponder the question again. Do not eat people. Eating people is wrong.
"Stick to plants and dead animals, steer clear of soylent green." Edward looked at the ceiling, no answers there. He put his head in his hands, no answers there. "I'd rather not be a murderer and I certainly hope you feel the same way." He looked into Bella's eyes and got no sign of comprehension. No sense of familiarity with the idea he had put forward. If it could have, his blood would have run cold.
[By the way, if this doesn't feel like it's set in a car that's because I completely lost track of time and space and thought that they were still in the restaurant when canon-Bella dropped that particular question and thus this is likewise set in the the restaurant. So, in addition to Edward being a very different person, this conversation is also in a somewhat different setting than canon.]