Even though we have no evidence that they even exist:
Drake is the man behind the Drake equation, the intellectual foundation of the six-decade-old effort to find technologically advanced alien life. At 89, he is still one of the most respected figures in space science. The search for aliens has turned up nothing thus far, but Drake says he has at least some idea of what space societies will look like. “In many, many places, evolution would produce intelligent species capable of making things,” he said, sitting in front of a mug of coffee in his California home, up the road from the beach amid millennium-old redwoods near Santa Cruz. “They will make technology we could detect from a great distance. That will be a common event. They will first make [primitive machines] and eventually radar transmitters, and once they make a radar transmitter, we can discover them.” Drake barely blinked.
Science cannot tell you the precise social details of an alien society — is there democracy? Do otherworldly beings go through courtship? But the principles governing atoms, chemistry, and fundamental forces everywhere can be used to infer its broad shape. If there are technological societies in space, for instance, the extraterrestrial population almost certainly lives in cities and uses language, since such cooperation underpins civilizations. Given that legislatures, iPhones, and Simone Bileses do not arrive from nowhere, its population is the beneficiary of competition and cooperation. There would have to be politics and war, since that is how disputes are resolved. There would be a locus of power in the form of leadership. That leader — a monarch, a parliament, a president, whatever — would be tribal and territorial, since a society is a coherent group with boundaries, even if there are divisions within it, according to Nicholas Wright, a neuroscientist at University College London.
Steve LeVine, “Why life on other planets will resemble ours” at OneZero
So if aliens exist, they must be just like us because… evolution. This is a religion.
Didn’t say it was a bad religion. But definitely a religion.
See also: Tales of an invented god