Any individual might be free to buy or sell or participate or not, but if there's some covert support, monetary or regulatory or informational, then the market isn't working according to the participant's input.
A firm offering worse prices to consumers, but getting inside information might drive its competitors out of business, even if they offer superior service or value. The outcome is different. I don't see how re-defining a free market in terms of the participant's choice makes it work like a market in which the government agency hasn't meddled.
It's not re-defining what a free market is, that's always been the case.
I guess the point I haven't got across is that even if the government interferes covertly with one specific product or market, it has little effect on the overall market. Just think of the number of SKUs in an average Walmart and you'll get an idea of what I mean.
It's a matter of degree. There is no 100% free market - your transactions are influenced by a lot of factors, from the taxes in Nicaragua to your physical location. Government intervention is one of those limiting factors; mobsters demanding protection money from a shop owner is another.
We (libertarians) prefer the markets to be as free as possible (with an ideal of 100% free) because we've seen a direct relationship between market freedom and economic prosperity (utilitarians) and / or because we find it more moral than the alternative.
A firm offering worse prices to consumers, but getting inside information might drive its competitors out of business, even if they offer superior service or value. The outcome is different. I don't see how re-defining a free market in terms of the participant's choice makes it work like a market in which the government agency hasn't meddled.