The economy objection
"Animal exploitation is big business. If everyone went vegan, the economy would collapse."
Problem 1: even if that happened, the world would have much less suffering and death. Economic losses don't compare to trillions of lives.
Problem 2: the idea is false. The economy doesn't depend on one specific industry. When people stop spending money on one thing, they spend it on another. New businesses pop up: plant-based foods, new technologies, other services.
The jobs objection
"People who work in animal exploitation would lose their jobs."
Problem 1: the harms don't compare. Losing a job is bad. But it's nowhere near comparable to spending your life suffering and then being killed. Giving more weight to the smaller harm just because the bigger harm falls on animals is speciesism.
Imagine humans were raised to become food. It would be ridiculous to say, "We can't end this, because the workers would lose their jobs."
Problem 2: the change is gradual. The transition would take years, giving people time to switch fields. This has happened many times: jobs disappear and others appear, as happened with typists and lamplighters.
In short
- The economy adapts: money gets spent on other things.
- Losing a job doesn't compare to a life of suffering and death.
- The change would be gradual, with time to create new jobs.