It is generally agreed upon that in a salary capped league, and especially in basketball wherein a single player has a disproportionate impact on the outcome of a game, salaries are depressed in comparison to what teams would pay for his services on an open market. Lebron guarantees a competitive team no matter where he plays and significantly increased revenues and franchise values when leaving for Miami and returning to Cleveland.
I joke sometimes that its the intersection of nominally left/liberal American pundits with sports fans. The political blog Lawyers Guns and Money being a good example of it-people you wouldn't think would have those views, but when it comes to professional sports, all of a sudden self proclaimed socialists love themselves a free market.
It's not a love of the free-market that drives these conversations; it's a hatred of exploitive capitalism. Ultimately, the players are source of all the league's revenue, yet the have to split that money with the owners (who contribute almost nothing to the day-to-day revenue stream).
The players also have a strong union, which negotiates a number of protections for the players, from minimum salaries to safe work conditions, while allowing for higher compensation for key players.
So it is very reasonable for those of us on the left to be against the extreme labor exploitation represented by the salary cap.
Theoretically it's possible. Realistically no. The leagues vote on team ownership transfers, and they are unlikely to allow a sale that upsets their apple cart. Which is why only one team (Green Bay Packers) out of the big three sports is owned by a government body.