I’m going to go out on a limb here.
First, I have no idea what they were dealing with or how vicious the attack was or what the situation was so they might have been justified but, in general, if a couple of cops cannot disarm a man with a broom stick they probably should not be on patrol. This would never fly if a service member shot someone, even in a combat zone, who was carrying a stick. In fact, sporting a weapon without intent to use that weapon does not give a service member permission to fire on them, according to the ROE. Why are cops held to a much lower standard?
The job of policing, as I understand it, is not merely showing up and shooting whatever problem you encounter. If it were, then just about any marksman could do the job. People here would be more upset if it was another officer dog shooting. Yes it is a nasty job but don’t sign up for it if you aren’t willing to get nasty with nasty people.
You mean that just wearing the enemy uniform (unless in full surrender mode) is not cause enough to kill them? Some ROE we've got here!