Oh, I see where you are coming from. I looked at Job 1:6 and Job 2:1 while trying to follow what you are saying.
But if mighty men were created by the sexual union of fallen angels and the fair daughters of men (they weren't) -
and if somebody wants to justify the belief that "sons of God" means "fallen angels" - then why is Satan excluded from their group in the book of Job?
Now there was a day when the sons of God came to present themselves before the LORD, and Satan came also among them.
Something more like,
"the sons of God, of whom Satan is chief (or even included)" even though it sounds, as my children would say, "wrong" would force me to see their point, but that's not was was said at all. So if "sons of God" does not include Satan, or fallen angels, then the conclusion that they must be that part of the group who had sex with pretty (fair) daughters of men is simply false. Sons of God means those who share their nature with The Father in heaven, not those who oppose Him.
As far as the discussion about what Jesus said regarding angels and sexuality - it is the only place in the bible that deals both clearly with the issue. The discussion was about a different false belief - the Sadducee thought there would be no Resurrection and proposed the dilemma. As if to say, "If there even is such a thing as a resurrection, what about the Law of Moses that directs us to marry our brothers widow? What would happen?"
"Whose wife would she be?"
Jesus addressed the main point saying that there wasn't sexual relations in heaven like there was on earth - and they had made a mistake because of two things - One, they didn't know the Scripture and two, they didn't understand the Power of God. They also misunderstood the purpose of God, supposing that God was a god of the dead. We are being created in order to be with Him; to be united with Christ (our Bridegroom). This is the Biblical mystery that Paul talks about, not a false, mystical, ancient Hebrew belief about angels.
The church isn't going to have sex in heaven. After the resurrection, the risen will not marry nor be given in marriage. They (hopefully we) will be like the angels (in this manner).