We're so quick to frame crabs as cruel for pulling each other down when they try to escape buckets, yet we too rarely focus on the person who put them in the bucket in the first place.
The same goes for the idea of mantises eating the heads of their mates (apparently an artifact of lab conditions) and of the "alpha wolf" idea (wolves were forced into the company of unfamiliar wolves), among other facets of "common knowledge."
How many assumptions about human behavior follow this pattern?