The problem here is that you need to use your imagination and play the what-if game to find the imminent threat. They set a trap and played it smart. They did it at a time when there were no civilians around for him to threaten, no chance for him to escape, and no imminent threat to them or himself since he had his back turned. The fact that they played it this way is smart, but it also makes it easy to argue that the use of force itself was objectively unreasonable under the circumstances, because they intentionally set up the circumstances so that he couldn't threaten anyone. The only part you can second guess is the decision to take the guy out, and there's not enough in the video for me to chew on regarding that topic.
As for who is right and the morality of it all, this kind of thing tends to split pretty predictably around whatever your personal/group opinion about cops is. Some Harvard assholes did a study about a famous Supreme Court case with similar facts where they sided with the cops. "Three law professors created an experiment based on the video, showing it to over a thousand subjects and then asking them whether they thought the use of deadly force was reasonable. The study found "[a] fairly substantial majority did interpret the facts the way the Court did. But members of various subcommunities did not." I think that's duckspeak for "the urban market" as Rok calls it, but you get the point.
