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.
2017-10-22 Rerun commentary: And we all know how that turned out...  If not, go read the plot summary. Or better yet, see the film.  It's getting to the point where sometimes when I reference things that I think everyone should know, people look at me funny because they've never heard of the thing I just referenced. This seems to be a hazard of getting older in a world where other people are born after you. See, in my head, everyone knows the stories of the most significant science fictions films of the 1950s and 1960s (even though they were released before I was born). So when I reference them, I expect people to get the references. And when they don't, I feel old... I guess "current popular culture" is a more of fixed-width window that slides along the decades, rather than an ever-growing extension into the future with a beginning point that everyone knows. I suppose the generation before me is appalled at my lack of knowledge of 1930s and 1940s popular entertainment.  Unfortunately there doesn't seem to be any viable alternative choice.