"This is the image we want to project to terrorists... if you are hiding in a Mosque and shooting at us; you will die!"
it all depends how we handle this at home. If we go stupid and prosecute the Marine we will be giving the wrong message to your enemies. If we don't, we'll send them a message that their days are numbered.
The West in general seems to adopt the philosophy that repayment cannot be made in coin minted by the terrorists or whoever because it would be "descending to their level". It has always seemed flawed to me, this supposition that we should "know better". That can be interpreted by the enemy only as a weakness to be exploited at every opportunity.
I'm so desperately sorry to hear of the "anger in the Arab world". It seems highly selective in causes for its indignation. What of the recent so-called "executions" of innocents - even aid workers? Going back, the Arab world didn't go puce-faced when Saddam Hussein was threatening it at the Arab Summit prior to the Gulf War, demanding billions of dollars for fighting what he called "their war" against Iran! (That was when he boasted of his "Al- Kimawi al Muzdawaj" - chemical arsenal.) Was there a tide of outrage shortly afterwards when he rammed home his threat by sending a Boeing to Cairo? Unexpected, the airliner landed carrying the bodies of Egyptians working in Iraq who had been tortured, shot and flown home.)