It's a funny world we live in. Colbert has an opinion on whether or not what is revealed in that video is murder. He's entitled to it. Strange to see him step out of character; this, I take it, was a bridge too far, a crime too great to ignore: calling soldiers who fired round after round onto people attempting to load the wounded into a van and get them medical attention "murderers," well, that's past irony and shtick. That requires open and unequivocal condemnation.
It's funny-- I consulted older videos of Colbert, online. He has spoken to members of Congress who voted for the war in Iraq several times. He has interview many who were involved in the apparatus of enacting the Iraq war, or who lent their considerable influence to the war effort. He has interview, that is to say, the people who created the material conditions where the victims of this attack were placed in harms way, where the soldiers involved were placed in danger of losing both their lives and their moral integrity. That's war, I'm told; you shouldn't wage it without being willing to risk atrocity.