First, that's a real misrepresentation of the kind of people and interests the NFU represents. Second, they can be wrong about one thing (right to roam) and still right about another (inheritance).
The National Farmers' Union, which you'll hear from a lot opposing inheritance tax, is not on the side of ordinary Brits. It acts more like a land owners club.
See this from them, opposing access rights (via the Right to Roam campaign)