Genesis 6:4 "The Nephilim were on the earth in those days, and also afterward, when the sons of God came in to the daughters of men, and they bore children to them. Those were the mighty men who were of old, men of renown."
The reference "sons of God" was the family root phrase in the Bible for the people of Israel to read about their origins as being of the line of Seth.
Luke 3:38 Which was the son of Enos, which was the son of Seth, which was the son of Adam, which was the son of God.
It was and can never be a reference used for angels, let alone fallen ones.
Matthew 22:30For in the resurrection they neither marry, nor are given in marriage, but are as the angels of God in heaven.
Only God can join a man & a woman in marriage and for these women to be called "wives" in the Bible to these sons of God, then they were not angels nor fallen ones.
If you consider how God did not want Israel to marry outside of Israel, then you can see why the Genesis account would emphasize the importance of it as their were giants in their early history wherein David slew Goliath. There is no scripture to verify that Goliath was the result of a former godly man of Israel with a non Israelis woman other than Genesis 6:4, however, since God can foreknew the results of His actions, if defeating "Satan's plans" to pollute the bloodlines was true, then flooding the earth would make God look kind of stupid so that cannot be the reason why He did it.
God said why He did it before the flood and after the flood.
Genesis 6: 1And it came to pass, when men began to multiply on the face of the earth, and daughters were born unto them,
This sets the precedent about how man was multiplying on the earth.
2 That the sons of God saw the daughters of men that they were fair; and they took them wives of all which they chose.
The word "That" as used above is in reference to that precedent mentioned in the first verse.
3 And the Lord said, My spirit shall not always strive with man, for that he also is flesh: yet his days shall be an hundred and twenty years.
It is the result of marrying outside of the line of Seth that God made this decree about man.
4 There were giants in the earth in those days; and also after that, when the sons of God came in unto the daughters of men, and they bare children to them, the same became mighty men which were of old, men of renown.
Do note the results of these unions as being referred to as men still.
5 And God saw that the wickedness of man was great in the earth, and that every imagination of the thoughts of his heart was only evil continually.
Do note the real reason above as to why Gid flooded the earth and not one mention of a polluted bloodline.
6 And it repented the Lord that he had made man on the earth, and it grieved him at his heart. 7 And the Lord said, I will destroy man whom I have created from the face of the earth; both man, and beast, and the creeping thing, and the fowls of the air; for it repenteth me that I have made them.
I see no mention of the destruction of the fallen angels that made themselves flesh.
8 But Noah found grace in the eyes of the Lord.
Whew. That was close.
Now note again as God confirmed with a promise as to why He had flooded the earth.
Genesis 8:20 And Noah builded an altar unto the Lord; and took of every clean beast, and of every clean fowl, and offered burnt offerings on the altar. 21 And the Lord smelled a sweet savour; and the Lord said in his heart, I will not again curse the ground any more for man's sake; for the imagination of man's heart is evil from his youth; neither will I again smite any more every thing living, as I have done. 22 While the earth remaineth, seedtime and harvest, and cold and heat, and summer and winter, and day and night shall not cease.
So the pollution of the bloodline by fallen angels is a myth of man following after the mythologies of the Greek gods & the Norse gods.
Now while some will strain at the gnat & swallow a camel whole by using "sons of God" as a reference for angels and yet fallen angels in the book of Job... it opposes itself.
#1) How can sons of God be still used as a reference for fallen angels that gave up their first estate? Answer: it cannot.
#2) If sons of God was a reference to angels and marrying women for them to be called wives to them means that God joined them together, then does that not make God an accomplice in this sin? Answer: yes: and so God would not do that. We all know that presently, when a man is joined to a man in marriage or a woman is joined to a woman in marriage that God is not joining them at all. It is not a marriage in God's eyes. Jesus said what a marriage was.
Matthew 19:4 And he answered and said unto them, Have ye not read, that he which made them at the beginning made them male and female, 5 And said, For this cause shall a man leave father and mother, and shall cleave to his wife: and they twain shall be one flesh? 6 Wherefore they are no more twain, but one flesh. What therefore God hath joined together, let not man put asunder.
So why would God have these women called wives to angels that will make them fallen angels? Answer: the sons of God cannot be angels nor fallen ones.
#3) Out of the two gatherings of the sons of God mentioned in the book of Job, Job was pointed out & mentioned twice, thus highly indicative that he was among the sons of God presenting themselves to the Lord. The descrepancy later on in Job was a misreading of God being sarcastic to Job on how the sons of God which Job was among them, had sung songs of worship testifying about His creation in the mornings when these sons of God have gathered together in presenting themselves to the Lord.
There would be no point mentioning that to Job unless he was a witness against himself and thus should know better especially since he has sung those songs too.
#4) The Hebrew text for "sons" of the phrase "sons of God" is "ben" which means a builder of the family name: hence of the line of Seth that Israel can relate to.
Those that still contend do so by ignoring the words of Jesus Christ & the Bible.
1 Timothy 1:4Neither give heed to fables and endless genealogies, which minister questions, rather than godly edifying which is in faith: so do.
1 Timothy 4:7But refuse profane and old wives' fables, and exercise thyself rather unto godliness.
2 Timothy 4:3 For the time will come when they will not endure sound doctrine; but after their own lusts shall they heap to themselves teachers, having itching ears; 4 And they shall turn away their ears from the truth, and shall be turned unto fables. 5But watch thou in all things, endure afflictions, do the work of an evangelist, make full proof of thy ministry.
Titus 1:13 This witness is true. Wherefore rebuke them sharply, that they may be sound in the faith; 14 Not giving heed to Jewish fables, and commandments of men, that turn from the truth. 15 Unto the pure all things are pure: but unto them that are defiled and unbelieving is nothing pure; but even their mind and conscience is defiled. 16 They profess that they know God; but in works they deny him, being abominable, and disobedient, and unto every good work reprobate.
I had believed such falsehood, but the Lord as my Good Shepherd, had set me straight. May He do the same for those inquiring on this subject for the truth.