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Now that Iran knows this, why should they cooperate?
If criminals from across town kidnapped your neighbours, would you rule out the use of force to get them back? You'd certainly hope that the police would negotiate, but you wouldn't mind if the police crashed through the door to get them back safely either. Just imagine if cops weren't allowed to use force. The real bad guys out there would ignore them.
Yet when thugs from across the world kidnap their marines and sailors, the British expect Iran to give up just because they're nice?