Evolution produced humanity. As a result humans are violent and react badly to foreign and unusual circumstances.
A planet where life arises and competition between such life forms does not occur would be unfathomable. All species compete for resources against all other species.
Humans have made many advancements. Yet they have carried the ancient suspicions, hatreds, and flaws forward with them. War is still a reality. Violence is an everyday occurrence. Competition is fierce. Hatred of what is different is glaringly present. Tolerance, much ballyhooed, is of scant supply even in those that promulgate it.
Although it is more likely humans will encounter machines from other civilizations rather than living forms, even those machines may carry the baggage created by evolution, it having been bequeathed by their creators.