Had you looked more carefully at what Jude wrote, then you could see that Jude was speaking of angels that "forsook" .........
These rebellious angels left their "proper dwelling place" in heaven as spirit "sons of God" and then came down to the earth, materializing as men and "committed fornication excessively" with women, which is "unnatural", or "in the same manner" as the inhabitants of Sodom and Gomorrah.(Gen 19:4, 5)
Yeh, it says "angels"alright, but it does not say "sons of God", two different classes of heavenly hosts. The "sons of God" should not be equated with the rebellious "angels", scripture in Psalms & Job makes it clear that the "sons of God" have always lived with God in heaven and were part of the heavenly host standing with God when Satan made his appearance in heaven to accuse Job. These "sons of God" in the book of Job also stood with God to praise the creation of the universe, these are not "angels" & it cannot be demonstrated by any scripture it is otherwise.
The "sons of God" in Gen 6 are "sons" of the earthly rulers (elohim) who are listed in Gen 5, just drop the capitalization on "God", make the "G" smallcase as it should be, then reread the scripture in the context in which it was written, should be written as: "sons of god". Just because you see the English word "God" for the Hebrew elohim, doesn't mean in Hebrew you are referencing the "elohim" in heaven, there are lots of "elohim" on Earth who are also "rulers" & they are all flesh & blood born of fathers & mothers just like you and I. And by the way, thus is why they had the ability to procreate with the daughters of other men, you know, just like you & me, our wives were once another man's daughter.
At Job 38, our Creator, Jehovah God , said to Job: "Who is this that is obscuring counsel by words without knowledge?....Where did you happen to be when I founded the earth?....When the morning stars joyfully cried out together, and all the
sons of God ("sons of God", Hebrew
beneh´ 'Elo·him´; Jewish
Targums, "the bands of angels"; Greek
Septuagint, "my angels) "began shouting in applause? "(Job 38:2, 4, 7)
Thus, at the laying of the foundation of the earth, the angelic hosts applauded, for no humans existed at that time, these being "sons of God" as Adam at Luke 3:38 and of which the apostle Paul said that Jesus, after his resurrection to heaven, continued to be called "the Son of God".(Heb 4:14)
At Psalms 89, the question is asked: "For who in the skies can be compared to Jehovah? Who can resemble Jehovah among the sons of God?" (or angels, Ps 89:6) And at Job 1, it says: "Now it came to be the day when the sons of ("sons of ", Hebrew
beneh´; Greek
Septuagint, "angels.") the [true] God
entered to take their station
before Jehovah, and even
Satan proceeded to
enter right among them."(Job 1:6)
The apostle Peter said that after Jesus resurrection, that "he went his way and preached to the spirits in prison, who had once been disobedient when the patience of God was waiting in Noah's days, while the ark was being constructed."(1 Pet 3:19, 20)
Hence, the "sons of God" at Genesis 6 are
not "sons" of the earthly rulers who are listed in Genesis 5, but rather are angels that left their "own proper dwelling place" in heaven, forsaking it, and materialized as men to commit fornication excessively with women.(Jude 6, 7)
These are later called demons ("demon", Greek
dai´mon, Matt 8:31), "wicked spirits" (Greek
poneron pneumaton, Luke 7:21; 8:2) and "unclean spirits".(Greek
pneumaton akatharton, Matt 10:1) The men of the cities of Sodom and Gomorrah followed after their pattern (Gen 19), going "out after flesh for unnatural use".(Jude 7)