Well, five minutes into the first segment Mr. Taggert stumbles. Human women had sex with fallen angels, not demons (Gen. 6:4). He is saying that the offspring that turned out large and god-like were the offspring of the fallen angels, and the monsters were the offspring of demons. This isn't accurate according to the Bible nor the Book of Enoch. Demons didn't come into the picture until much later.
When the great flood came and destroyed the Nephilim on the earth, their souls could neither ascend to heaven nor descend to hell. They were consigned to wander on the earth.
1 Enoch 15: 8-12
8. And now the giants, who have been begotten from body and flesh, will be called evil spirits on earth, and their dwelling-places will be upon the earth.
9. Evil spirits proceed from their bodies; because they are created from above, their beginning and first basis being from the holy watchers, they will be evil spirits upon the earth, and will be called evil spirits.
10. But the spirits of heaven have their dwelling-places in heaven, and the spirits of the earth, who were born on the earth, have their dwelling-places on earth.
11. And the spirits of the giants, who cast themselves upon the clouds, will be destroyed and fall, and will battle and cause destruction on the earth, and do evil; they will take no kind of food, nor will they become thirsty, and they will be invisible.
12. And these spirits will rise up against the children of men and against the women, because they have proceeded from them, in the days of murder and destruction.