"In actual reality you will never have any certainty about the outcomes of interactions like these. All you have control over is whether or not you hurt the person in front of you."

Errr I think you're "proving too much" so to speak. Having someone in front of you who you know has details about a terrorist plot that could stop it, and you think finding those details is something you can't reason morally about? By your definition of certainty, you basically can't do anything with any degree of certainty unless its actions are immediate.

Call up an assassin and tell them to murder someone? Well who knows if she'll even go through with it, so that's morally fine.