I do feel the farmers have picked the wrong fight.
It seems they feel that they should be compensated for poor income by being given allowences on the capital value for inheritance purposes. Why? This does not help them improve their income, or make it easier to improve their return on capital which is currently so low for many.
If the IHT was 100% the cost of land would drop like a stone as it would no longer be a tax wrapper and those purchasers would have to look elsewhere. There would be positive outcomes from this.
Currently, the cost of land excludes the purchase by younger farmers who cannot borrow to invest if the can't show the business can make the acceptable return on capital. The aging of the workforce will not help in food production.
With the land use returning to farming, rather acting as a tax shelter, farmers can fight the real fight. I don't believe this will be easy. Farming income has been difficult since the 1960's and 70's when Resale Price Maintenance was removed and first Convenience Stores, then Supermarkets appeared. Brexit has only added to many of their woes.
The buyers power to negotiate by comparison to the farmers power has beaten farmers income down. I doubt anyone would suggest its return to RPM, nor are we likely to return to the EU. However, somehow farmers need to take, or be given, a more equal negotiating position. That is the fight they should be having.