we have a population of 8 billion people. right now killing them [edit the cows] is necessary because people are eating them. price adjustments get people to eat them less, meaning less of them have to die. you take steps in the right direction, people voluntarily make the choices that get themselves eating less meat.

the world where people do not eat meat is a fantasy. you've got to realize that. however, giving the animals that will be eaten better lives and providing an economic framework that all but ensures fewer animals will be eaten, that's realistic.