I'm not sure what the content of "making your opponent behave (ir)rationally" is >supposed to be. It's certainly not an uncontroversial tidbit of received wisdom that the >rational thing to do in the Prisoner's Dilemma is to defect, which is what you seem to >imply.

Exactly, if I was able to make him act irrationally, he would not defect, whereas I would. And if the definition of rationality is that it makes you win, then it can be perfectly rational to have others act irrationally (i.e. believe wrong things).