That's not how it works. There is no fair share. He is saying that farmers are not actually paying the costs they make society incur. Therefore these costs are not priced into the meat they produce which would not be that competitive if that was the case. It's a form of subsidy.

If the external costs were included, consumer would simply be forced to pay for their consumption.

This would give a fair advantage for food that has less external costs.

External costs are also hard to estimate, especially if they is burdened on another species. How much is the suffering of a chicken worth?

So then you get back to the original condition - subsidizing food once again. In fact, this is the reason why they are subsidized in the first place!

If a less lucky person (or what you call poor) receives money, they are still incentivized to spend the money efficiently. With the money they have available now, they can buy less meat but more plant based food than before.

Meat would then become slightly more expensive than plant, but also have a major benefit for products that don't use a lot of water or harms the soil. Aquaculture would get a big boost, as would alternative method of meat production. The use of farm animals as an ecological alternative to using machinery to keep land clear of unwanted vegetation has become a niche method, and increased water and soil regulations would indirect benefit such farming alternatives.

Please, every time someone proposes farmers lead a less cushioned life we get these huge bitter fights from somewhere. They don't also have to exist here. If you have a vested interest and want your subsidies to continue, that's cool! But there's no need to peddle your salty response to it when literally everyone everywhere has already heard them said many, many times.

Jesus Christ... Come spend a week on my farm and see how cushy it is.

Edit: Besides that, a subsidy is a cushion. That's what I was talking about. That doesn't merit this response.