The ED-209 offscreen killing of a kid just because he has a knife despite the fact that it wouldn't do anything is subtle evidence to support the logic behind the Dreyfuss act, that being a robot doesn't possess the morality and empathy necessary to effectively judge people as a human does. That, and it shows that while the ED-209 isn't the complete joke it was in the original Robocop movies (the original was so pathetic it couldn't go down a flight of stairs without falling), neither is it completely effective either.
Alternately: the ED-209 wasn't viewing the kid as a threat to itself, it did see it as a threat to nearby civilians. A steel knife may not be able to leave a dent on a robot, but it can easily go through human flesh.
There were also high-priority civilians nearby marked by red tags. That might have overridden some of the possible restrictions.
The reason they keep Murphy's right hand. It seems pointless to save such a small scrap of Murphy compared to the rest of his new body. But consider his weapons. The gun he keeps for his right hand is a high tech stun pistol. It has functions of incapacitating to killing its target. It has control over if someone lives or dies, and it's in Murphy's human hand. Omnicorp knows how to subtly market things.
It's also been pointed out that the right is the one you shake with, representing the merging of man and machine. Sellars played a part in this. In one of the deleted scenes, he asks point-blank if the right hand can be salvaged, because his father always said you can learn a lot about a man from his handshake. Again, marketing, but with lots of symbolic overtones.
Iran is occupied by a drone army that can potentially gun down civilians for comparatively trite reasons, like the kid with the knife. The rest of the world is okay with this it seems. Did Iran do something bad enough to warrant this, or did the world just not care?
Or has OmniCorp's combat drone development turned America into such a superpower that no one is willing to stand against them with anything less than a full nuclear strike?
Honestly, the biggest Fridge Horror is this is not really an exaggeration as RL Drone strikes kill civilians (let alone a Loophole Abuse enemy combatant like the kid) all the time on faulty data.
RoboCop's body can be completely shut down, leaving him paralyzed, a mutilated man trapped in a robotic shell. He's completely helpless. That's already pretty bad, but keep in mind this version of RoboCop still has his real face and lungs. If RoboCop had landed on his front instead of back when they shut him down in the rice fields, he would have drowned in the dirty irrigation water.