[xorfish]

Demand for food is pretty inelastic.

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?

[chii]

and yet if you actually did that, people on the other side of the political spectrum would complain that it's unfair for poor people because they now have a higher food cost burden. Shouldn't the rich subsidize for the poor for these essentials?

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!

[xorfish]

No, if you implement a efficient system to transfer wealth, you don't subsidize meat as meat and plant based food are treated equally.

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.

[belorn]

We could for example lower taxes for those that earn least while increasing water and soil quality regulations (with matching tariffs for imports). This would increase food costs, which would hopefully match the money that people gained through lower taxes.

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.