I would prefer to discuss the reasoning that the "sons of God" were mortal men in genesis 6. It would be more interesting.
The Hebrew phrase "sons of God" in this passage, and elsewhere in the Old Testament, can refer to angels (Job 1:6; 2:1; Psa. 29:1; 89:6). But the same phrase elsewhere in the Old Testament describes humans who lived their lives in service to God (Deut. 14:1; 32:5; Psa 73:15; Hosea 1:10). In the New Testament the term "sons of God" is applied exclusively to humans (Matt. 5:9; Rom. 8:14, 19; Rom. 9:26; II Cor. 6:18; Gal. 3:26).
Fallen angels or demons are not called "sons of God" anywhere in the Bible.
Speculation that what is being spoken of in Genesis 6:2 is fallen angels ("supernatural beings," i.e. "gods") fathering children with women amounts to nothing less than a blatant intrusion of pagan superstition into the Bible, a superstition that finds absolutely no support, real or imagined, in the rest of Scripture.
The Bible calls angels "ministering spirits" (Heb. 1:14), and it tells us that "a spirit does not have flesh and bones" (Luke 24:39). That being the case, angels who do not possess human flesh could never have fathered human children. A simple biological reality which I tend to believe even the ancient writer of Genesis understood.
Jesus told us that angels do not marry. (Mark 12:25) Yet that is just what the "sons of God" in Gen. 6:2 are said to have done. So, unless Jesus had never read Genesis, it seems unlikely the "sons of God" there referred to were angels. If they were, how would the writer of Genesis conclude that Noah's flood would have stopped them from continuing their "skirt chasing" after the flood? Maybe he thought that spirits/angels/demons can be drowned. Besides, why would fallen angels have been interested in a monogamous "marriage" relationship? If these are fallen angels being spoken of in Gen. 6, wouldn't we expect the writer to tell us of their seducing or raping women rather than "marrying" women?
This "sons of God" = "fallen angels" understanding of Genesis 6:2 makes no sense for several reasons.
What Gen. 6:1,2,4 records is the first occurrence of mixed marriage between believers and unbelievers, with the all too common result of such unions. Children raised with lower moral standards. In other words, the "sons of God" in this passage were descendants of the godly line of Seth. Instead of remaining true to God and loyal to their spiritual heritage, these "sons of God" allowed themselves to be enticed by the beauty of ungodly women who were mere "daughters of men."
But why would the fact that normal men started noticing pretty women be recorded? Why should that be noteworthy enough to get mentioned at all?
It was the lowering of moral standards in the land of Noah, which was largely the result of worshippers of the true God marrying worshippers of false gods, which caused God to bring judgment upon the people of that land by means of a great flood.
