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The alien being named Klaatu visits earth and stresses the urgency of the reason for his visit to earth with the words, "I want to meet with all the representatives of the nations of the world" and "the future of your planet is at stake."
Notice that through the particular camera angle it appears that Klaatu is speaking from above down below to his earthly listener. The effect of this cinematographic trick is to give Klaatu the appearance of having superior authority.
While referring to Klaatu, two medical officers examining him, discuss his age:
"How old do you think he is? Oh I'd say 30, 35. He told me this morning when I was examining him; he's 78. Life expectancy is 130. Their medicine is that much more advanced."
This leaves the viewer with impression that (regular) medicine is the key to not only restoration of health but also to longevity itself. By associating medicine with longevity the viewer is helped to place a religious kind of trust in the medical establishment. It is therefore not a stretch to think that the commercially dedicated medical industry, most notably its pharmaceutical branch, loved the fact that propaganda as featured in this scene was being shown, seemingly free of charge, to by-and-large gullible audiences.
No doubt, little did the typical viewer of the 1950s know that decades later it would turn out that regular medicine can easily be proven to be more of a risk factor to health and longevity than it is an unquestionable boon to health and well-being and a sure way to life extension as the movie would like to have the viewer believe.
A further irony shown by this scene emerges at its conclusion when both officers are about to light a cigarette, a habit that of course works precisely to oppose longevity, although at the time it was probably still not a medically established fact that indeed smoking cigarettes precipitates premature death.
Indeed, the association of longevity and smoking, combined with the lack of understanding that smoking antagonizes good health and longevity, can even be interpreted to mean that the latter works to accomplish the former. It can be imagined that this would very much please the tobacco industry.
In this scene you see Klaatu and his juvenile companion named Bobby visit Arlington's war cemetery. Since the planet where Klaatu comes from do not engage in warfare, he asks young friend in a state of bewilderment: "Did all those people die in wars?"
The impression on the viewer is that the place Klaatu comes from must also be a serene place where people are happy and are barren from urges to go out as barbarians trying to kill one another for some petty reason. Since most if not all well-thinking people just want peace and tranquility, Klaatu's voice gains more authority through recognition.
"What do you think it makes it go?" Bobby asks Klaatu. "A highly developed form of atomic power, I should imagine", Klaatu suggests.
Thus a link between a high standard of technological advancement, represented by the mysterious and impregnable flying saucer, and atomic energy is suggested to the viewer. Or rephrased, it is suggested to the viewer that an advanced level of technological development is predicated on the utilization of atomic energy.
It thus sounds like great advertisement for peddling atomic energy to the public. An idea that is perhaps not so far-fetched since atomic energy was still in its infancy and the public still needed to warm to the idea of benevolent applications of atomic energy as only a couple of years prior, thousands of people had been obliterated by atomic weapons.
Here you see the first meeting taking place between Klaatu and Professor Barnhardt (an obvious personification of Albert Einstein). Klaatu confesses to the Professor:
"So long as you are limited to fighting among yourself with your primitive tanks and aircraft, we were unconcerned. But soon one of your nations will apply atomic energy to space ships. That will create a threat to the peace and security of other planets. That of course we cannot tolerate."
He then explains to Prof. Barnhardt that hostile attitudes in outer space will not be tolerated and non-compliance to rigid universal laws will be met with sure annihilation of Earth:
"I came here to warn you that by threatening danger, your planet faces danger, very grave danger."
It should be mentioned that through the ease by which Klaatu successfully helps the professor, touted as the smartest man in the world, in solving a most difficult physics problem he was stuck at, it is clear that Klaatu has more than just marginal intellectual dominion over the professor and, by extension, the entire world.
Combined with the particular use of cinematographic techniques, such as Klaatu's insistence to remain standing after he had been requested to sit down by the Prof. and thus is looking down on him together with the authoritative manner in which Klaatu addresses the submissive professor, it is further emphasized to the viewer that Klaatu not only possesses intellectual but also moral superiority akin to the kind parents naturally have over their children.
It should be noted that throughout the movie, the military can be seen to be present everywhere in rural areas while busily interfering with civil life. These can be perceived to be birth signs of a sure police state. It is to be expected though that the military's presence and interference with civil life is likely to be rationalized as being necessary to warrant state security, a notion that is likely to have been in need of popular familiarization since the passing of the National Security Act of 1947.
The military, while having assumed the role of regular police, proceeds with using deadly force without issuing prior warnings or invoking attempts to apprehend and arrest suspected law violators.
Near the end of the movie, Klaatu explains in full his motive to visit Earth:
The universe grows smaller every day, and the threat of aggression by any group, anywhere, can no longer be tolerated. There must be security for all — or no one is secure... This does not mean giving up any freedom except the freedom to act irresponsibly. Your ancestors knew this when they made laws to govern themselves — and hired policemen to enforce them.
We of the other planets have long accepted this principle. We have an organization for the mutual protection of all planets — and for the complete elimination of aggression. A sort of United Nations on the Planetary level... The test of any such higher authority, of course, is the police force that supports it. For our policemen, we created a race of robots — Their function is to patrol the planets — in space ships like this one — and preserve the peace. In matters of aggression we have given them absolute power over us. This power can not be revoked. At the first sign of violence they act automatically against the aggressor. And the penalty for provoking their action is too terrible to risk.
The result is that we live in peace, without arms or armies, secure in the knowledge that we are free from aggression and war — free to pursue more profitable enterprises. Now, we do not pretend to have achieved perfection, but we do have a system, and it works. I came here to give you these facts. It is no concern of ours how you run your own planet, but if you threaten to extend your violence, this Earth of yours will be reduced to a burned-out cinder. Your choice is simple: join us and live in peace, or pursue your present course and face obliteration. We shall be waiting for your answer. The decision rests with you. Source
The comparison with the United Nations is interesting and seems to have been somewhat in vogue during those days as the movie Things to Come (1936) can also be considered to be a UN advertisement.
The viewer is thus nudged into accepting the idea that freedom (to act irresponsibly, supposedly) is better to be traded for security lest witnessing Earth ultimately transform itself into a "burned-out cinder." And of course, as the movie hints at, the answer to capping our dangerous barbaric tendencies lies with accepting the United Nations as the necessary and desired sociopolitical straight-jacket that should keep us from harming ourselves.
Along the way, the notion of a robotized police enforcement is given a big welcome, something that again would welcomed with the advent of later movies such as Robocop.
Note that Klaatu again speaks with confidence and steadfastness while he addresses the Earthly intellectual elite from up above, thus once more reaffirming his authority over them similar to a group of submissive children sitting on the ground looking up to their parent who is reading out loud some weighty tale of morality to them.