> 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.