1 Martian 1: You have a suggestion, Earthling?
1 Ishmael: Yes.
2 Ishmael: Drop your giant machines of war in the Middle East and warn of humanity wiping itself out and being unable to join galactic society unless we learn to live in peace and harmony.
3 Martian 1: Drop our giant machines of war...
4 Martian 1: {to Martian 2} Take a note. We should look into getting some of those for our next invasion.

A common trope of science fiction of the Cold War era was the arrival of powerful alien beings who proceeded to either: deliver dire warnings that humanity has to learn to grow up and get along with itself or risk annihilating itself; or forcibly intervene in human conflict with their advanced technology that renders our own puny instruments of war ineffective. Either way, the lesson was clear: get over our petty squabbling and act like a united species, or risk destroying ourselves.

Probably the most iconic such story was The Day the Earth Stood Still.