"Why won't you?"
"I don't eat meat."
"You don't??? Since when?"
"All my life"
"I never even knew that, you never bring it up."
"No, I don't."
"Well, you know, vegetables have feelings, too."
"And leather is made of animals, too."
"Which is why I don't wear it."
"And you know, everyone has to be happy with themselves. I mean, where would it stop. And besides, you drink milk. bla bla bla bla bla bla bla." (10 minute tangent about the pleasures of eating meat, social responsibility, eco footprints, etc.)
Lunch over. Maximun level of annoyance. Rinse. Repeat.