Why? Formotiis is a DEMON, no shit. He is evil in flesh, evil is in its own constitution so he loses because it is its nature.
Loptyr no. He was an Earth Dragon (and maybe not naturally evil like Formotiis) that got so salty that he would need to live in human form that he decided to conquer humanity and create a slave holding empire that sacrifices kids to him.
The reason for child sacrifice? Spite. He gets nothing of it but pleasure at seeing 'those stupid monkeys' that would inherit the world instead of his own race suffering. Because y'know, humans are to blame.
That is some level of spitefulness that can only rank high there. And since Jugdral is Akaneia in the past...I get why humans hate dragons.
Look to Loptyr. He gave them all a bad rep.