Us humans, we can do anything. I can't, for the life of me, remember the source of the quote, nor can I the quote itself, but on Star Trek, probably Deep Space Nine, there was a quote about humans that's stuck with me. You take 10 Klingons, you've got 10 fierce warriors. 10 Ferengi, you've got 10 shrewd businessmen. 10 Romulans, 10 expert spies. But you take 10 humans, you don't know *what* you're dealing with. They could be anything.What you get is ten bigots. Because, see, humans, specifically the humans that wrote that script, look at ourselves as "people" and the other people, the ones with the pointy ears or the furry feet or the bony ridges on their foreheads, as "archetypes".
All Klingons are honor-loving warriors. All dwarves are beer-swilling Lawful Good blacksmiths with, for some reason, bad fake Scottish accents. All elves are ethereal granola-munching bunny-hugging archers. But humans are people and therefore can be good or evil, horticulturalists or mechanical engineers, priests or physicists, saints or monsters.
In Dungeons & Dragons, dwarves can't be rangers and halflings can't be magic users, but humans can be any character class. In Star Trek, the United Federation of Planets is a galaxy-spanning polyspecies polity, but the officer's mess on any Starfleet vessel looks more like a board meeting at Augusta National than it does the cantina in Star Wars. The most homogenous, conformist technological society on planet Earth has everything from tattooed yakuza to sumo wrestlers to lolita cosplayers, but you could title a documentary on Klingons Fifty Shades of Worf.
A perceptive Younger Me would have tipped to this earlier, and maybe wondered if it had any application in the real world whenever I heard "All men are..." or "All redheads are..." or "All Chinese people are..." Ah well, we live and we learn. Or at least one would hope that we do.