Then Callahan says:
This is a very good point. Libertarians might consider that it applies every bit as much on the attempt to force free trade or unregulated labor markets on society as it does to force collectivized agriculture on society. (italics added)I'm not sure how you force free trade since free trade would be the natural state. Limits on those freedoms would be the result of force.
Now, Callahan makes a good point about guilds which can be the product of free people freely associating. Unfortunately, the lesson of history has been that those same guilds would use their clout to lobby their governments to restrict others freedoms. Today we call them special interests; steel, sugar, corn, oil, etc..
I've no problem with free people freely exercising their right to freedom of association to freely practice their freedom of speech. Just don't inhibit my freedom to freely trade.
That's a mouthful of freedom.