So, there's this race of higher beings, but humans believe them to be some kind of monsters. The creatures are believed to be extinct in the present day, but the bad reputation has stayed. The belief itself is sorta false, since the creatures are not evil - the only part that is true is the amount of destructive force.
How can this belief hold up?
Maybe some of them could be corrupt or something that look like them did some damage
They could be falsely accused of a crime or something
Well, I have something similar that I am writing about. For me, I have them be the gentle giant look. They look scary as all hell but do not harm. There are plenty or myths and stories that have been made from a small, short glance at an object or animal and have made them monsters over time.