The problem with the nitrate pollution is, that everyone in the affected area is paying for it. They are paying for it, by requireing extra steps to clean the water before it is drinkable, by causing more cancer and other diseases straining the healthcare system and ultimately by destroying the soil so much that the agriculture will just fail at some point and then relying on 100% imports.
The farmera rallying against it are extremely selfish, and worse they are on a path of destroying themselves and taking the entire country with them.
No loss in market value can be relevant enough to permanently destroy your countries ability to grow food.