A long time ago, some Demons turned themselves into human men.
They did this to be able to have relations with women way back then.
The women gave birth to the Demons babies and they grew to be giants.
Any child that came from a Demon was most likely dispicable and defiant.
I honestly believe that one of the Demons children was Goliath who was a giant.
Many people were afraid of Goliath but it was just a child who killed the evil tyrant.
Demons can no longer become human men like they did thousands of years before.
God put an end to it, Demons can't turn themselves into human beings anymore.