The movie is similar to another common ethical dilemma in which you are a time traveler who has the opportunity to kill Hitler while he's a child. Would it be moral to kill him before he actually committed his crime, even if you were as certain as you could be of what his future held? Can the ends justify the means? Can one be guilty and justly judged before they've committed a crime?
Minority Report and time traveling assassins are all far-fetched sci-fi concepts, but the idea of preemptive justice is not far-fetched at all. As Americans, we've preemptively judged many nations through our military and many criminals through disproportionate sentencing. We drop bombs and we raise sentences based on what we know of our enemies.
While we certainly preemptively judge on a national scale, we Americans often promote Minority Report justice on an individual scale. I mean, isn't that what self-defense usually is? If someone invades your home and you choose to confront them with a gun rather than lock your room and call the police, aren't you preparing to kill an aggressor based on the assumption that they're seeking your harm rather than your material goods? Even if one thinks the death penalty is a legitimate punishment for murder, how many cases of "self-defense" are cases in which one's life would have been taken? How many times is self-defense taking the life of someone who would have stolen or assaulted rather than killed?
I have to ask two questions, then. First, why are we so critical of Minority Report as being Orwellian when we do something similar in our promotion of self-defense on both a national and individual scale? Second, why do we hide our inhumanity behind self-defense? Many would be appalled at state execution for theft, assault, or rape, as many are even appalled at state execution for murder. Yet self-defense goes even further in that it is execution for a presumed crime.
Self-Defense is passing the death sentence for a crime not yet committed.