If you further accept the argument below that LDT is a better candidate than CDT for the principle of rational choice, then it is also fair to say that economists should stop going around proclaiming that rational agents defect in the Prisoner's Dilemma\. LDT is not a polyanna solution that makes Cooperation right for almost everyone almost all the time\. Two LDT agents might end up Defecting against each other, e\.g\. because they don't know each other to be LDT agents, or don't know the other knows, or don't have a quantitatively great enough trust in their ability to predict the other accurately, etcetera\. But "rational agents in general just can't do anything about the equilibrium where they defect against each other in the oneshot Prisoner's Dilemma" is much too harsh; e\.g\. it seems readily solvable if two rational agents have common knowledge that they are both rational\.
Two L's