If everyone becomes a vegetarian, won’t this create economic hardship for those who depend on animal agriculture?
Yes, if everyone becomes a vegetarian, then many people who depend on animal agriculture will have to find a new way to earn a living.
Several hundred years ago, many people’s jobs and economic well being depended on the continuation of the slave trade. Nevertheless, the ethics of the situation dictated that the slave trade should be abolished, even though this meant that these people would have to find a new way to earn a living.
There is nothing new or unusual about the process of an entire industry disappearing. For example, people who worked in the horse carriage industry needed to find new jobs after cars were invented.
Quote by Eugene Khutoryansky
Indeed, but this is part of life. Change is what moves the world forward. As BeeTooman posted, the trading of slaves was once accepted as a way to earn a living, and many people were in hardship after this ended. Certainly no one would doubt that ending slavary was the right choice because, of course, slavary is immoral, 
ing, and wrong. I would say that farmers who grow plants and fruit would end up benefiting, and the people who did work in animal agriculture would have the chance to earn a living in a way that is cruelty-free.
If they are in animal agriculture, then they could simply plow some fields and start making their money on raising vegetables. Or tear down their pens and plant some fields there if they don’t have enough field space.
There are lots of alternative… They may switch to other businesses and jobs… I think this would be good… A longer life span… 