Why is the average farmer tax-exempt?
1. They aren't.
2. A large majority of farmers have farm incomes of circa 17,000pa. From that money comes basic expenses to run a farm, none of which non-farmers face. The average worker earning 17,000 would not out of that have to pay vet's fees, Artificial Insemination fees, maintenence fees for a farm yard, the cost of buying farm animals and/or harvesting crops, the costs of hay or silage, the costs of running a tractor, the costs on occasions of hiring labour, plus insurance costs for the farm, its buildings, its animals, etc.
3. A significant minority have incomes below the minimum wage.
4. A small minority have very large incomes. Urban dwellers think the large ranchers are typical of the average farmer. They could not be more wrong. That is like thinking that the pay to the Board of Directors of the Bank of Ireland is typical of the wages of Bank of Ireland employees.
IF farmers were all creaming it and making a fortune, the number of farmers would be doing up. Instead they are in freefall. It doesn't take a brain-surgeon to see why.
You want farmers to pay income tax? Fine. Give them an income to pay income tax on.
Your post is the standard moan that comes from people who haven't a clue about the realities of the agricultural economy.