
Originally Posted by
Random
That is a human tribal response.
It has nothing to do with stereotypes.
When we don't understand something completely we turn the things we don't understand into "Them" and all of "Them" "Do the same thing" because our experience is so limited.
Sci-fi isn't written with psycho-analysts directing the plot. It's written by "normal" people generally. People whom don't realize this tribal characteristic being played into their fiction.
So basically that is why any stereotype exists. Lack of understanding. If the creatures written have a pre-canon background that is diverse you almost always lose that "all the same". See>Farscape.