1) It looks to me that a Marine killed an unarmed terrorist.
2) Sites knew the video would aid the Terrorist cause.
"We all knew it was a complicated story and, if not handled responsibly, could have the potential to further inflame the volatile region."
3) He also knew it was not "typical" Marine behavior.
4) He could have used the video to pursue justice within the military. It did not have to be reported to the world.
5) Sites had the option. He chose to cash in. He knew it would damage the Marines, he knew it was not typical, but it must be reported. It didn't have to be reported. Notice he never mentions how much he got paid. He can talk about his journalistic imperitives but leaves out how the money influences his decision.
The money influenced his decision.