Recognizing the impossibility of planned economies does not require advocating deregulation. This is first of all clear from the terms: “a planned economy” presupposes that there is “an economy” as a quasi-organic or at least intelligible whole while regulation needs to assume no such thing. Again, planned economies are fair only on some theories of justice while regulation is necessary on any theory. For Americans, the terms are also significant since the Constitution makes no reference to “the economy” while it marks out areas for regulation.
The easy slide from “no planned economy” to “deregulation” skips over why one would deregulate at all. Adam Smith had a clear vision of the world he was shooting for in a free market: maximized competition in order to cultivate the virtues of moderation, foresight, creativity, etc. But maximizing competition is something that requires a great deal of oversight, insight, and intervention. Just glance at the power and extent of Olympic regulatory agencies.
Free markets are competitive, but there’s an infinite distance between judges and referees allowing persons to compete with each other and the same judges announcing “Anything goes!” The point is not to caricature positions but to suggest that the analogy between fair competition in markets and sports suggests that fair markets require a massive amount of what will seem to everybody as invasive meddling.