> There's only one way to treat a counterpart who repeatedly defects on the iterated prisoners dilemma, and its not waiting for them to unilaterally start cooperating.

Except that there isn't only one way, there are two. The first is that you keep playing with the defector and start defecting yourself, hoping that they unilaterally start cooperating. The second is that you quit playing with the defector and go play with someone else. And which one of those is likely to work out better for you?