Did we cross a line by not capturing an unarmed suspect, but instead, summarily shooting him in the head?
Maybe this was a big favor to the world. If Bin Laden had been taken alive, the amount of media time spent on every little detail about Bin Laden would have dominated the news for far too long. It is possible that hostages could have been taken in exchange for the release of Bin Laden. And, at every step of trial process, threats would probably have been made.
And yet, there's something about shooting an unarmed man without a trial, that just seems wrong.