Judge Dick Posner on Kelo and Guns

I was reading Dick Posner's recent piece in the New Republic on the Heller case, and I have to admit I am quite puzzled by his arguments. Take this comment about Kelo:

Another illuminating contrast to Heller is the recent Kelo decision. The Supreme Court held that the just compensation clause of the Fifth Amendment does not forbid a state to condemn private property and, having thus seized it, to turn it over to a private developer. The decision provoked outrage by conservatives, who oppose condemnation because it infringes rights of private property. They should not have been outraged. All the Court did was unshackle government from a potential constitutional constraint, and by doing so toss the issue into the political arena. And sure enough, in the wake of the decision a number of states, under pressure from property interests, curtailed their eminent domain powers. . . .

"All the Court did was unshackle government from a potential constitutional constraint"? If you took this approach across the board, it is not clear what the point of a constitution would be. How can a constitution protect a minority if it merely tosses questions back to the political arena?