As you've correctly pointed out, you don't have to buy anything from him.
But if you are buying organic milk, you are willingly, though indirectly, buying from him or guys like him. They are the ones who produce and sell the outragously priced organic feedstuffs to the dairy.
Just think, each bushel of wheat deliverd to that dairy has 1 gallon of fuel used just to make that final delivery. This happens month after month.
And don't think for a moment he doesn't appreciate it. He really wants that new tractor.
That's the beauty if the free market. I can buy from whomever I please, even fictitious relatives of people who make stuff up trying to defend bloated, government subsidized farming. And I really don't care. I make enough money to buy the things I please. If I want to feed my son milk without synthetic hormones in it, that's my business. But I don't have to passively accept comments from people who declare I am dependent on Monsanto to eat. I can call it baloney, because it is.