> Seems like a pretty standard "free markets/Econ 101" argument to me.

Hm I think I see what you mean. It's a free market argument that includes that some regulation is in place which keeps A in business and keeps D out of business.

But wouldn't the free market corollary then be to remove that regulation so the market can be more free? That's hardly the suggestion coming from the left-leaning perspective, which instead proposes to add more regulation. So the end-to-end argument (including s corollary for what to do) doesn't actually sound free market to me.

Indeed, free market means no Government intervention such as price controls and anything else that distorts the market.

And it is not exactly "left" either. Rothbard was a right-libertarian, aka. libertarian capitalist or right-wing libertarian.