However, understanding that in a free society the government is always in a position to decide what agreements it is willing to enforce in the interest of the free market. Without a system where disputes can be equitably resolved, private agreements are either not free or not effective.
Once you have third parties deciding what contracts between consenting adults are and are-not void, you -- by definition -- don't have a "free market" any more... Either they are all valid and enforceable or there is no enforcement at all.
In a free market there is either "enforcement of all contracts and agreements" or "no enforcement of such". As soon as a third party gets to pick and choose which contracts and agreements are enforced, the free aspect of the free market is removed, because *really* every agreement exists at the whim of an unrelated third party.
There is no possibility of a free market without rules governing the free market which keep it free.
The only "rules" that are even theoretically necessary are ones ensuring that all agreements and contracts are enforced. ALL, except in the presence of actual fraud (which, let's be clear, is not at issue here, but is in your shopkeeper example).
I agree with those that say the lack of competition is the real underlying issue, but you need rules to address that. I am not talking about more or less rules... just the right rules for the free market system we want.
And what I said elsewhere was that the right way to handle this -- in a way that both solved the problem and was pro-free-market -- was to have regulation which specifically attacked the actual problem -- competition. We've had 20-30 years of forced lack of competition, so another 20-30 years of, say, forced bundling should give "upstarts" the access to outside plant they need to start turning a profit, to the point where they can start either buying the infrastructure from incumbents, or building out infrastructure of their own.
You respect the free market process, you create actual competition, and you have a path towards removing the "outside third party" from interfering in folks' right to negotiate with each other for goods and services.