But building AI isn't the same as defecting in the Prisoner's Dilemma because it risks harming the defector too, if there is loss of control.

If we're talking game theory, a better model is the Stag Hunt [1]. At some point the equilibrium strategy is to cooperate.

Another difference is that real life is an iterated game, and the iterated prisoner's dilemma rewards cooperation.

[1]: https://en.wikipedia.org/wiki/Stag_hunt