I'm not on the up and up about military regulations and what soldiers can and can't do. However, that said, I have two points.
First, our soldiers may be ambassadors, but I believe this took place with a bunch of guys and no civilians. As a result, even assuming a grunt should have the responsibility of being an ambassador (which is debatable in another conversation) he certianly wasn't wearing his ambassador hat at the time and thus shouldn't be held to that standard.
Secondly, granted the information age has changed things, but how many of us have done things in front of a camera, stopped and thought about the potential for it becoming plastered all over the internet. Probably none other than the most paranoid. Even if his buddy told him, "yeah I'm gonna put this on my webpage" who has the kind of foresight to think about whether or not it might be front page news. Nobody. Why? Because we all lead uninteresting lives that nobody, least of all the major news media, wants to know about.
Is it the brightest moment in this kids life, probably not. But then again if you're getting shot at so I can sit here and waste time posting on a gun board, I'm gonna give you a hell of alot of leeway in what you say and do.
Probably the most important thing about this is the fact that no one was harmed. I can't remember the quote or who said it, but the essence of it is that people can say anything they want, but words simply can't hurt you. That is true here. For those that use this as an excuse for violence against us, they would have found something else had this not happened.
As for the hearts and minds, that really doesn't matter at all. As I have said before, I don't care if you love me or even like me. All I care about is that you respect me. At the end of the day thats all that matters. If we set the proper tone we will be respected. Unfortunately it hasn't happened yet.